In 1934 Ataturk wrote a now famous tribute to the soldiers killed at Gallipoli:
"Those heroes that shed their blood and lost their lives ... You are now lying in the soil of a friendly country. Therefore rest in peace. There is no difference between the Johnnies and the Mehmets to us where they lie side by side here in this country of ours ... You, the mothers who sent their sons from faraway countries, wipe away your tears; your sons are now lying in our bosom and are in peace. After having lost their lives on this land they have become our sons as well."
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Westminster Abbey
During the Westminster Abbey service the high commissioners of Australia and New Zealand, Alexander Downer and Sir Lockwood Smith respectively, gave readings from the Bible. Turkey's Ambassador Abdurrahman Bilgic read the famous message from Mustafa Kemal Ataturk modern Turkey's founding father, to bereaved pilgrims who visit the Gallipoli battle sites.
Prayers were said by young people from New Zealand and Australia and like many of the memorial events today the Last Post was sounded.
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Westminster Abbey
The Queen arriving earlier at Westminster Abbey. As the congregation sang the hymn 'O valiant hearts, who to your glory came' the national flags of Australia, New Zealand, Turkey and the UK were carried through the church and placed close to the high altar as a sign of reconciliation between old enemies.
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Westminster Abbey
The Queen and Prince Phillip have just left Westminster Abbey at the end of the Gallipoli service.
Dean of Westminster
At the beginning of the service the Very Reverend Dr John Hall, Dean of Westminster, said in his bidding: "The landing of allied forces at Gallipoli exactly 100 years ago today led to one of the bloodiest battles of the First World War."Alongside forces from Britain and her allies, troops from Australia and New Zealand fought together as the Australian and New Zealand Army Corps: ANZAC."We honour today the courage of the men at Gallipoli."
@RealTimeWW1
tweets: Afternoon tea instead of battle: Brit. sailors are off for picnic, Imbros island.#Gallipoli100 http://goo.gl/FkPWHl - a respite from the campaign
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The tomb of the unknown warrior
The tomb contains the body of a unknown serviceman of the British Empire who was brought from France and buried in great state at Westminster Abbey on 11 November 1920.
The idea for the tomb came from the Reverend David Railton who was a chaplain on the front line.
tweets: Fantastic #Gallipoli100 commemorations all day today. Thanks to crew of #HMSBulwark for their hospitality and role
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Westminster Abbey
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tweets: Her Majesty The Queen and HRH The Duke of Edinburgh arrive for the #ANZACDay2015 service @BritishMonarchy pic.twitter.com/9PWhaEeo9P
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Westminster Abbey, 1916
The Times reported that several hundred survivors from the Gallipoli campaign were present at the Abbey. It noted that the soldiers "all looked cheerful and hearty" despite some having lost limbs or their sight.
Most of the Abbey was filled with soldiers as well as army chaplains. The choir was reserved for relatives of the fallen and distinguished guests including the Archbishop of Canterbury, Lord Kitchener and Australian Prime Minister Mr Hughes.
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The service of thanksgiving and commemoration at Westminster Abbey is being attended by Australian and New Zealand expatriates.
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London embraces first Anzac Day, 1916
The Times recorded an emotional crowd gathering by the Abbey overflowing with "joy and pride in these men from the Dominions who had won fame on impossible battle grounds".
It went on: "When the King and Queen arrived the pressure was so great that the police were carried off their feet and the people nearly reached the Royal carriage."
Nigel Farage
Earlier, UKIP leader Nigel Farage stood with veterans and members of the armed services as he attended the ceremony to mark the 100th anniversary of the start of the Gallipoli campaign, at the Cenotaph, on Whitehall in London.
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King George V marks first Anzac Day
99 years ago today the Queen's grandfather, King George V, attended the first Anzac Day service at Westminster Abbey.
It was held in honour of "our brothers who died at Gallipoli for their King and Empire, in the high cause of Freedom and Honour".
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Queen arrives
The Queen has arrived at Westminster Abbey.
NZ Youth Ambassadors
tweets: A lovely service at Chunuk Bair, with fitting addresses from the Turkish Ambasador and the Prime Minister #ww100 #Gallipoli100
NZ Defence Force
tweets: Beautiful melancholic note perfect Last Post played by CPL Kevin Hickman at Chunuk Bair Anzac service #Gallipoli2015 #Anzac100
Westminster Abbey
Commemorations in the UK to mark the centenary of the start of the Gallipoli campaign will conclude with a service at 13:00 BST at Westminster Abbey. The Queen will lay a wreath at the tomb of the unknown soldier.
He gave a rousing speech in London, saying: "On this day, called Anzac, the Australasian soldier leapt unheralded into the arena of war."
Some veterans, such as the New Zealander Captain Turnbull, felt "Anzac Day" underplayed the role of their British and French allies at Gallipoli.
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Evacuation
The Allies decided to pull out of Gallipoli in November 1915. They disguised their withdrawal by using tricks such as spacing out their artillery fire.
Half of the forces were evacuated from the peninsula in December and the last men left on 9 January, 1916. Careful planning meant there were only three reported casualties from the evacuation.
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Clegg and Miliband
Deputy Prime Minister Nick Clegg and the Labour leader attended the memorial ceremony at the Cenotaph.
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Kensington Palace
tweets: Prince Harry reads an extract from a letter by an unidentified member of the Canterbury Mounted Rifles #Anzac100
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The beginning of the end
Field Marshal Lord Kitchener, commander in chief of the British Army, visited the Anzacs at North Beach in November 1915.
He spent two hours surveying the Turkish line from Australian trenches inland of the Sphinx and at Lone Pine. After speaking to commanders on the ground, he recommended to the British War Cabinet that the peninsula be evacuated as little progress could be made without major reinforcements.
NZ Defence Force
tweets: Lovely to have their Royal Highnesses Prince Charles and Prince Harry at the NZ Chunuk Bair Anzac service #Anzac100 #gallipoli2015
John Key
Prime Minister of New Zealand
tweets: "For New Zealanders, nowhere in Gallipoli is more special than here on Chunuk Bair." #ANZAC100
Clarence House
tweets: The final service Their Royal Highnesses are attending for #Anzac100 is at Chunuk Bair, the New Zealand memorial
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Turkish ambassador
Abdurrahman Bilgic, the Turkish ambassador in the UK, speaks during a wreath-laying ceremony at St Paul's Cathedral earlier.
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Scottish ceremony
Nicola Sturgeon, the First Minister of Scotland, lays a wreath at a special ceremony to mark the Gallipoli centenary at Edinburgh Castle.
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New Zealanders at Chunuk Bair
Chunuk Bair bore witness to a courageous stand by New Zealand forces during the offensive of August 1915.
They were ordered to capture and hold the strategic summit, which they did during a desperate struggle. They were relieved by British troops and the summit was lost shortly after during a determined Turkish counter-attack.
It was the closest to a breakthrough the Allies achieved in the whole campaign.
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Prince Harry and Prince Charles are attending their final service as part of the Gallipoli commemorations. It is at Chunuk Bair, the New Zealand memorial.
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Temporary truce
Fierce attacks and counter attacks in the first few months of the Gallipoli campaign left soldiers' corpses exposed to the elements in no man's land.
On 24 May, the Allies agreed to a one-day truce to allow both sides to bury their dead, as the summer heat had caused the bodies to rot, causing an unbearable smell.
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The Allied force in numbers
The Allied forces were commanded by Briton Sir Ian Hamilton. Most of his overall force of 75,000 men were on the Peninsula by mid-May.
In August they were joined by 60,000 more men at Suvla Bay. In December 1915 to January 1916, 105,000 men were evacuated from the Peninsula.
Among those watching the ceremony were 10-year-old Edward Jackson, wearing the medals of his great grandfather, Commander Arthur Mallet, who served in the Royal Navy and was injured during the campaign. Near the Cenotaph, artist Nadir Imamoglu, born in Turkey but living in the UK for 40 years, has set up a sculpture based on a larger one he has created at the National Memorial Arboretum in Staffordshire. It is made of young oak trees- to reflect the ages of the men fighting at Gallipoli - the bare branches reaching into the sky. The sculptor explains this represents the arms of those injured in battle reaching out for help.
Daniel Boettcher
BBC News
Before the wreath-laying ceremony those gathering to take part heard music led by the massed bands - pieces drawn from some of the countries that took part in the Gallipoli campaign. Those waiting along Whitehall to lay their wreaths listened in silence - service personnel, veterans of more recent conflicts, members of military associations including the Gallipoli Association. Also present were descendants of those who fought in the campaign.
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The Cenotaph ceremony is concluding with a march past.
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Turkish pride
The defending Turkish troops were driven by a grim determination at Gallipoli. The 19th division were led by Lt Col Mustafa Kemal, who later founded modern Turkey.
He told his officers: "I don't order you to attack - I order you to die. In the time which passes until we die, other troops and commanders can take our place."
At Anzac, Kemal's forces held on to the high ground and stopped the Australians and New Zealanders from advancing. They also stopped Allied forces advancing north of Krithia in Helles.
From 1916, street shrines began to appear. A year later, the Imperial War Museum was founded to record the conflict for future generations. The Imperial War Graves Commission (IWGC) was established to record the deaths and mark the graves of those who had fallen.
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Here is Michael Toohey, wearing his fallen relative's medals.
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Michael Toohey, 22, was among the young people to give a reading at the Cenotaph. His great-great uncle died on the first day of the Gallipoli campaign and Michael was wearing his medals.
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Leaders
In addition to the Prime Minister David Cameron, Labour leader Ed Miliband, Deputy Prime Minister Nick Clegg and UKIP leader Nigel Farage were also present at the Cenotaph ceremony.
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Shell shock
Soldiers experienced severe psychological strain at Gallipoli, and many suffered from what we now know to be depression, anxiety and post-traumatic stress disorder.
Those with symptoms were said to have 'shell shock' as doctors first thought the conditions were caused by an invisible force from exploding shells.
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Poppies to remember
Poppies have been laid to remember those who were killed at Gallipoli.
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The Queen. Duke of Edinburgh and the Duke of Cambridge at the Cenotaph
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The scene at the Cenotaph in Whitehall, London.
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God Save Our Queen is sung at the Cenotaph.
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Wreath laying and readings have been followed by band music.
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The Turkish national anthem rings out at the Cenotaph.
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Guards stand near the Cenotaph as the ceremony's events continue.
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Following a prayer read by 11-year-old New Zealander, Kathryn Cooper, the New Zealand national anthem is played at the Cenotaph.
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Boy soldiers
In total, about 50,000 Australians were sent to Gallipoli. The youngest, James Martin, was only 14 years old. People were supposed to be 18 to enlist in Australia and 19 in Britain, but tens of thousands of underage soldiers managed to join up.
James died from typhoid fever in October 1915 and was buried at sea.
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The Australian national anthem is being played and sung at the Cenotaph.
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The Gallipoli Memorial, which commemorates all those who took part in the campaign, was erected by the Gallipoli Association and unveiled in November 1995 by Prince Philip in the presence of eight surviving veterans.
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Before the Cenotaph ceremony, the Duke of Edinburgh led the annual wreath-laying ceremony at the Gallipoli Memorial in the crypt of St Paul's Cathedral.
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A lasting memorial
The Cenotaph was designed and built by Edwin Lutyens to mark Peace Day events in July 1919. It was only supposed to be a temporary structure and was built from wood and plaster.
When unveiled in November 1919, the public spontaneously covered it in floral wreaths. It was so popular it was rebuilt a year later in Portland Stone to become a permanent and lasting memorial.
Peter Hunt
BBC Royal correspondent
tweets: Prince William is at the Cenotaph Gallipoli commemorations. Not yet at the private Lindo Wing. #RoyalBaby
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The Australian, New Zealand and British military are all represented at the Cenotaph ceremony.
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David Cameron followed the Queen in laying the wreath at the memorial.
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The Queen bows after laying the wreath.
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The Queen laying her wreath at the Cenotaph.
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Prime Minister David Cameron places the second wreath, followed by the representatives from Australia, New Zealand and Turkey.
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The Queen steps forward to lay the first wreath at the foot of the Cenotaph
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The Last Post sounds to mark the end of the silence
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The Queen is accompanied by the Duke of Edinburgh and Prince William
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The chimes of Big Ben mark the start of a two-minutes' silence.
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The Queen will lay the first wreath.
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British politicians are joined by Australia's attorney general and the speaker of New Zealand's House of Representatives as wreath bearers.
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Choristers at the Cenotaph
Choristers from Chelmsford have been singing at the Cenotaph.
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The wreath bearers emerge at the Cenotaph.
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Cenotaph service
The ceremony to mark the centenary of Gallipoli has started at the Cenotaph in London.
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Losing their bearings
The Allies had been issued with standard 1:40,000 scale maps for the attack. However, these failed to show important details of the hilly terrain. The heights given for many of the hills were also incorrect.
A group of New Zealanders heading from Plugge's Plateau to Russell's Top had to make an hour's detour into a valley because the map didn't show the two were joined by an impassable ridge.
By August the maps were gradually replaced by more accurate 1:20,000 maps redrawn from captured Turkish maps.
Clarence House
Prince Harry and Prince Charles in Gallipoli
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tweets: TRH visit the Nek Cemetery, where many Australians who fell in the charge of the 3rd Light Horse Brigade are buried
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The first days
Over three days British troops consolidated their position from the landing beaches to form a line across the tip of the Gallipoli Peninsula. However, they then failed to take the village of Krithia on the slopes of Achi Baba.
Achi Baba was their first-day objective but they failed to hold it during the campaign.
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Landing at Helles and Kum Kale
At Cape Helles, 3,000 Tommies landed at Y Beach, and some 15,000 landed at W, X, V and S beaches. Their objective for the first day was to secure Achi Baba, a ridge about a mile inland.
Around 3,000 French troops landed at Kum Kale on the Asiatic shore. This was a feint designed to confuse the enemy and draw off the long-range guns. A few days later the French joined the British at Helles.
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A nurse at Gallipoli
Sister Kathleen "Kitty" Mann was serving on the HMAT Ulysses and kept a diary on board:
"We lost a patient this morning after he had had two operations, poor boy, it was sad, only 24hrs, and he had been through so much (gas gangrene); it was horribly sudden.
"I witnessed a burial at sea for the first time that day. It was held on the end deck after lunch, the body being placed on a slanting board, covered with a union jack. The burial service was read by the Captain, there being no Padre; others attending were the OC Troops and some of the medical staff. It was most impressive and quite reverently done."
Nurse Kathleen Mann, 23 August, 1915. Extracts displayed at Hospital + Troop Ships exhibition on board HQS Wellington.
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Modern medicine
"To say that since writing last we have been through a literal hell is putting things very mildly."
Major Vivien Benjafield, of the Australian Army Medical Corps, IWM
Surgeons and nurses were severely tested by the ferocity of modern warfare, but the conflict also led to medical innovations.
Ed Miliband
Labour leader
tweets: Soldiers came from across the globe to stand with Britain in our nation's hour of need, and they must never be forgotten.
Ed Miliband
Labour leader
tweets: The centenary of Gallipoli is a moment for Britain to remember those who died in one of the First World War's most traumatic chapters.
Order of the day
The Lone Pine ceremony is concluding with the ceremonial laying of wreaths. British Foreign Secretary Philip Hammond is among those laying flowers at the memorial site. Shortly Turkey is to hold a service at the Turkish 57th Regiment Memorial on the peninsula, followed by a New Zealand service at Chunuk Bair, scene of a bloody battle for the imposing summit. At 1100 BST, there is a further service at the Cenotaph in central London, followed by a 1300 BST service at Westminster Abbey.
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Landing at Anzac
Some 12,000 men landed at Anzac (Z beach) on 25 April. Their objective for the first day was to secure the third ridge, later called Gun ridge, about a mile inland.
However, after the initial surprise, the well-prepared Turkish defences managed to contain the Allied troops. They were led by Mustafa Kemal who would later become the founding father of modern Turkey.
Lone Pine service
Australian PM Tony Abbott takes to the podium and pays his tribute: "To us they are Anzacs, but in their day they were fathers, sons, parents, children, cousins and mates just as you are now. You walk among their headstones, you read the inscriptions, you hear the epitaphs and you hear their families speak - in these inscriptions and in these epitaphs we hear the echoes of our country a century ago." You can watch the service by clicking on the Live Coverage tab at the top of this page.
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Prince Harry's address
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Prince Harry has begun speaking at Lone Pine: "In this quiet place it is difficult to imagine the carnage, the desperation of the fighting that took place here. But it was in this spot that many acts of valour took place, and despite the number of Victoria Crosses awarded for the fighting here, most of those acts went unrecognised. Great valour was a common virtue."
'One of bloodiest battles'
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Air Chief Marshal Mark Binskin describes Lone Pine as "one of the bloodiest battles in Australia's history". He tells the congregation: "The Gallipoli campaign exacted a heavy toll that left an indelible scar on our nation." Of the ordinary men who "found extraordinary determination" in the name of duty, he says "we honour them, and the actions that inspired the Anzac spirit".
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Lone Pine, August 1915
By summer 1915 there was a stalemate at Gallipoli. In August new offensives and landings were launched along the peninsula to try and break it.
At Lone Pine, Anzac troops fought a fierce three-day battle to take the pine-log covered trenches here. They sustained 2,300 casualties and won 7 Victoria Crosses in the action.
The New Zealanders briefly occupied the strategic high point at Chunuk Bair before misdirected friendly artillery fire and a Turkish counter-attack forced off the British and Gurkhas who had relieved them.
Veterans honoured
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There is a heartfelt round of applause at Lone Pine as all veterans present at the ceremony are invited to stand. The emotion of the occasion is clear on the faces of some of the 8,000 proud Australians attending.
St Paul's remembrance
As the Australian memorial service gets under way in Gallipoli, the Duke of Edinburgh, patron of the Gallipoli Association, is joining the congregation at St Paul's Cathedral for a service of remembrance in London.
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Light moment ahead of service
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Australian PM Tony Abbott and Prince Charles have chatted with members of the crowd gathered at Lone Pine ahead of the Australian memorial service. Both men had an early start today, addressing at a pre-dawn ceremony. Prince Charles spoke movingly about soldiers who were "tormented by the thought of their comrades being left behind" and that their graves would remain unvisited.
Watch: Lone Pine service
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The Australian Service is about to get under way at Lone Pine on the Gallipoli peninsula. You can watch live video from the ceremony by clicking on the Live Coverage tab at the top of this page.
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Treating the wounded
Nurses treated patients on hospital ships such as the converted HMHS Devanha off the coast of Gallipoli under risk of artillery fire.
Hospital ships were merchant vessels crewed by merchant seafarers, who were civilians.
They ferried the injured to hospitals on islands such as Lemnos and Malta as well as Egypt and England. If they died en route they would be buried at sea.
Do Australians risk Anzac fatigue?
Wendy Frew
Australia editor, BBC News Online
The Australian government is spending A$145m ($113m, £76m) on Anzac commemorations including building an Australian Remembrance Trail on the Western Front, refurbishing the Australian War Memorial and building a new Australian War Memorial in New Zealand. That compares with the £50m being spent by the UK government on World War One commemorations. Some are asking whether Australians risk Anzac fatigue.
Nightclub 'interrupts service'
The Sydney Morning Herald website is leading with the story of how Saturday's dawn services marking the centenary of Anzac Day were interrupted by music from a nearby nightclub several times. The owners of the club have apologised and blamed unauthorised sound testing for an event later in the day.
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Pictures from London service
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More pictures have been coming in from the Anzac Day Dawn Service at Wellington Arch in London. Princess Anne was among the dignitaries attending.
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Get involved
Email talkingpoint@bbc.co.uk
William in London writes: I will remember that my maternal grandfather, William Wright, served at Gallipoli in the Sherwood Rangers Yeomanry - he survived and was posted to Palestine. Two very important future leaders also served at Gallipoli: Prime Minister Clement Attlee and Field Marshal the Viscount Slim.
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Extreme weather
Soldiers experienced extreme weather in Gallipoli, with a heatwave in summer and a freezing winter.
"I woke up to the find the whole country white. It looks beautiful and covers over so many things which are not."
Private Ronald McInnis, 26th Battalion, November 2015, AWM
But many men were under-prepared for the cold conditions. A blizzard in November caused 160,000 cases of frostbite and 280 men froze to death.
Lone Pine service
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The BBC's Lucy Hockings is at Lone Pine cemetery which she said is filling with Australians ahead of a service of remembrance in a few hours time. Many of those gathering were up to attend pre-dawn services on the Gallipoli peninsula. In August 1915, the area was the scene of one of the bloodiest battles in Australia's history as the Anzacs pitched themselves against a series of formidable entrenched Turkish positions.
Watch: Drone video
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For an overview of the Gallipoli peninsula and the battle sites, watch this film made using a drone.
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U-boat threat
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Allied shipping was terrorised by German U-boats throughout World War One. At Gallipoli, the U-21 sank two British battleships in May 1915 - HMS Triumph and HMS Majestic, with the loss of nearly 200 men.
A dawn service attended by the Princess Royal is taking place at Wellington Arch in Hyde Park Corner, London. It's an annual event but larger crowds were expected this year.
At 11:00 BST there will be a wreath-laying ceremony and parade at the Cenotaph on Whitehall attended by the Queen, Prince Philip and the Duke of Cambridge, and at 13:00 BST a service of commemoration at Westminster Abbey.
Forgotten Indigenous soldiers
During World War One, Australia's Defence Act 1903 excluded people who were not substantially of European descent from enlisting, but some got round the rules.
Amid the slaughter and sacrifice at Gallipoli, stories emerged of resilience and mateship in the heat of battle. Labelled by journalist Charles Bean as the 'Anzac Spirit' it fulfilled a much-needed craving in Australia and New Zealand for a national identity.
tweets: 100 years later, bullets found on the beach at #Anzac Cove. #Gallipoli100
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Dawn attack
The Anzac Corps were the first Allied troops to land at 4.30am on 25 April, 1915. They were towed in chains of small vessels behind steam boats, before they rowed the final 50m (164ft) to shore.
The first troops landed unopposed but on the wrong stretch of beach, now known as Anzac Cove. They had intended to land a mile further south, which didn't have such a steep incline. Soldiers used their bayonets to start scrambling up the hill.
Dawn ceremony concludes
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The dawn ceremony is now over. Australians will soon move off to Lone Pine for a service starting in four hours while New Zealanders remember their dead at the other upper level battleground of Chanuk Bair.
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As it's almost completely light, the Last Post is performed. A minute's silence will follow.
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A prayer of remembrance and the Lord's Prayer were read before wreaths were laid.
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Prince Charles read the words of Lieutenant Ken Millar and Company Quartermaster Sergeant Benjamin Leane, written during the campaign.
'I died loving you'
Wendy Frew
Australia editor, BBC News Online
Like many Australians, I have ancestors who served in World War One. The stories of their military service are well known by my relatives and their diaries, letters and medals are precious family relics.
One of those letters — written by my great-great uncle, Benjamin Bennett Leane — was read by Prince Charles to the crowd gathered in the cold dawn at Anzac Cove.
Two days before the fateful morning when the Anzacs landed on the shores of Gallipoli, Benjamin, then a captain in the Australian army, wrote a letter to his young wife that he feared would be his last:
"Know that I died loving you with my whole heart and soul, dearest wife that a man ever had. Kiss little Gwen and our new baby, who perhaps I may never see, and never let them forget Daddy."
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The Allies had reached a stalemate on the Western Front by September 1914. A month later the Ottoman Empire formally joined the Central Powers, led by Germany, when it bombed Russian seaports.
Winston Churchill, then First Lord of the Admiralty, planned to knock the Ottomans out of the war by attacking the capital Constantinople.
The navy first had to force open a route along the Dardanelles by the Gallipoli peninsula. This was a total disaster. A larger land assault was devised in its stead.
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Australian Prime Minister Tony Abbott tells the thousands gathered at Anzac Cove on Turkey's Gallipoli peninsula, the men who left from "every rung of the ladder" became "the founding heroes of our modern Australia".
'Wipe away your tears'
A quotation by Mustafa Kemal Ataturk - the founder of the Republic of Turkey after the fall of the Ottoman Empire - is read.
"You, the mothers who sent their sons from faraway countries wipe away your tears; your sons are now lying in our bosom and are in peace.
"After having lost their lives on this land they have become our sons as well."
John Key address
John Key, prime minister of New Zealand, is making an address.
He says: "Time and perspective have cast the Gallipoli campaign in a different light but 100 years ago both sides were doing what they believed was right and necessary."
He salutes the bravery of all who have fought on the peninsula.
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Princes Charles and Harry are among a large number of international dignitaries and thousands of members of the public gathered in the dark in silence.
Call to Gathering
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The dawn service is due to begin shortly. We just heard a Maori Call to Gathering performed by women of the New Zealand Defence Force. You can watch the service on BBC News.
Roll of honour
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The names and epitaphs of the Australian and New Zealand soldiers who died at Gallipoli are now being shown on a big screen.
Ceremony begins
The Spirit of Place - preceding the dawn service - has begun with a didgeridoo performance and a soliloquy about the landing.
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What was Gallipoli?
The Gallipoli Campaign was an ambitious military operation in World War One to knock the Ottoman Empire out of the war.
The British and French-led force planned to seize the capital Constantinople (now Istanbul) by launching a land and sea assault from the Turkish Gallipoli peninsula.
They planned to advance 200 miles (320km) north-east to the capital but only succeeded in establishing a tiny foothold at Gallipoli.
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Among the dawn memorial events that have already taken place, images of soldiers were projected onto a building near the Cenotaph war memorial in Sydney.
Prime ministers unite
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tweets: Anzac spirit alive and well - on the bus to Gallipoli for the dawn service with @TonyAbbottMHR.
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Thousands of Australians and New Zealanders have waited overnight for the dawn service at the Anzac Commemorative Site in Gallipoli. To attend they had to enter a ballot.
What's planned?
In the next few hours a memorial dawn service will take place near to the site of the landings in Turkey.
Australia and New Zealand's prime ministers, Prince Charles and Prince Harry and 10,000 people are expected to attend.
Afterwards, Australians will walk to Lone Pine, the site of a battle where the country suffered more than 2,000 casualties.
Meanwhile, New Zealanders will attend a memorial at Chunuk Bair, a summit which was the scene of heavy fighting.
A dawn service will be held in London and a march past later at the Cenotaph.
Australia and New Zealand events
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Australia and New Zealand have marked the centenary of dawn landings at Gallipoli with memorial services.
Events in Canberra, Sydney, Brisbane and Melbourne were attended by thousands of people, as were similar events in New Zealand including a big ceremony in Wellington.
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About 131,000 troops - 45,000 Allied forces and 86,000 from Turkey - died at Gallipoli.
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Welcome to BBC News's live page marking the 100th anniversary of the Gallipoli campaign.
A series of events will be taking place on the Turkish peninsula on Saturday to commemorate one of the bloodiest campaigns of World War One.
Live Reporting
Alex Therrien and Trevor Timpson
All times stated are UK
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Latest PostEnd of live coverage
That ends our live coverage of today's commemorations of the centenary of the Gallipoli campaign in World War One.
Events in Australia, New Zealand, Turkey and the UK have been attended by thousands of people, as will as national leaders and military personnel.
Continue to follow the news story here.
Turkish Gallipoli division commander
In 1934 Ataturk wrote a now famous tribute to the soldiers killed at Gallipoli:
"Those heroes that shed their blood and lost their lives ... You are now lying in the soil of a friendly country. Therefore rest in peace. There is no difference between the Johnnies and the Mehmets to us where they lie side by side here in this country of ours ... You, the mothers who sent their sons from faraway countries, wipe away your tears; your sons are now lying in our bosom and are in peace. After having lost their lives on this land they have become our sons as well."
Westminster Abbey
During the Westminster Abbey service the high commissioners of Australia and New Zealand, Alexander Downer and Sir Lockwood Smith respectively, gave readings from the Bible. Turkey's Ambassador Abdurrahman Bilgic read the famous message from Mustafa Kemal Ataturk modern Turkey's founding father, to bereaved pilgrims who visit the Gallipoli battle sites.
Prayers were said by young people from New Zealand and Australia and like many of the memorial events today the Last Post was sounded.
Westminster Abbey
The Queen arriving earlier at Westminster Abbey. As the congregation sang the hymn 'O valiant hearts, who to your glory came' the national flags of Australia, New Zealand, Turkey and the UK were carried through the church and placed close to the high altar as a sign of reconciliation between old enemies.
Westminster Abbey
The Queen and Prince Phillip have just left Westminster Abbey at the end of the Gallipoli service.
Dean of Westminster
At the beginning of the service the Very Reverend Dr John Hall, Dean of Westminster, said in his bidding: "The landing of allied forces at Gallipoli exactly 100 years ago today led to one of the bloodiest battles of the First World War."Alongside forces from Britain and her allies, troops from Australia and New Zealand fought together as the Australian and New Zealand Army Corps: ANZAC."We honour today the courage of the men at Gallipoli."
@RealTimeWW1
tweets: Afternoon tea instead of battle: Brit. sailors are off for picnic, Imbros island.#Gallipoli100 http://goo.gl/FkPWHl - a respite from the campaign
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The tomb of the unknown warrior
The tomb contains the body of a unknown serviceman of the British Empire who was brought from France and buried in great state at Westminster Abbey on 11 November 1920.
The idea for the tomb came from the Reverend David Railton who was a chaplain on the front line.
It is a memorial particularly to World War One soldiers who have no known grave.
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Foreign Secretary Philip Hammond
tweets: Fantastic #Gallipoli100 commemorations all day today. Thanks to crew of #HMSBulwark for their hospitality and role
Westminster Abbey
tweets: Her Majesty The Queen and HRH The Duke of Edinburgh arrive for the #ANZACDay2015 service @BritishMonarchy pic.twitter.com/9PWhaEeo9P
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Westminster Abbey, 1916
The Times reported that several hundred survivors from the Gallipoli campaign were present at the Abbey. It noted that the soldiers "all looked cheerful and hearty" despite some having lost limbs or their sight.
Most of the Abbey was filled with soldiers as well as army chaplains. The choir was reserved for relatives of the fallen and distinguished guests including the Archbishop of Canterbury, Lord Kitchener and Australian Prime Minister Mr Hughes.
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The service of thanksgiving and commemoration at Westminster Abbey is being attended by Australian and New Zealand expatriates.
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London embraces first Anzac Day, 1916
The Times recorded an emotional crowd gathering by the Abbey overflowing with "joy and pride in these men from the Dominions who had won fame on impossible battle grounds".
It went on: "When the King and Queen arrived the pressure was so great that the police were carried off their feet and the people nearly reached the Royal carriage."
Nigel Farage
Earlier, UKIP leader Nigel Farage stood with veterans and members of the armed services as he attended the ceremony to mark the 100th anniversary of the start of the Gallipoli campaign, at the Cenotaph, on Whitehall in London.
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King George V marks first Anzac Day
99 years ago today the Queen's grandfather, King George V, attended the first Anzac Day service at Westminster Abbey.
It was held in honour of "our brothers who died at Gallipoli for their King and Empire, in the high cause of Freedom and Honour".
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Queen arrives
The Queen has arrived at Westminster Abbey.
NZ Youth Ambassadors
tweets: A lovely service at Chunuk Bair, with fitting addresses from the Turkish Ambasador and the Prime Minister #ww100 #Gallipoli100
NZ Defence Force
tweets: Beautiful melancholic note perfect Last Post played by CPL Kevin Hickman at Chunuk Bair Anzac service #Gallipoli2015 #Anzac100
Westminster Abbey
Commemorations in the UK to mark the centenary of the start of the Gallipoli campaign will conclude with a service at 13:00 BST at Westminster Abbey. The Queen will lay a wreath at the tomb of the unknown soldier.
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How April 25 became Anzac Day
The Australian Prime Minister, William Hughes, championed the ordinary soldier and threw his support behind establishing the first Anzac Day in 1916.
He gave a rousing speech in London, saying: "On this day, called Anzac, the Australasian soldier leapt unheralded into the arena of war."
Some veterans, such as the New Zealander Captain Turnbull, felt "Anzac Day" underplayed the role of their British and French allies at Gallipoli.
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Evacuation
The Allies decided to pull out of Gallipoli in November 1915. They disguised their withdrawal by using tricks such as spacing out their artillery fire.
Half of the forces were evacuated from the peninsula in December and the last men left on 9 January, 1916. Careful planning meant there were only three reported casualties from the evacuation.
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Clegg and Miliband
Deputy Prime Minister Nick Clegg and the Labour leader attended the memorial ceremony at the Cenotaph.
Kensington Palace
tweets: Prince Harry reads an extract from a letter by an unidentified member of the Canterbury Mounted Rifles #Anzac100
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The beginning of the end
Field Marshal Lord Kitchener, commander in chief of the British Army, visited the Anzacs at North Beach in November 1915.
He spent two hours surveying the Turkish line from Australian trenches inland of the Sphinx and at Lone Pine. After speaking to commanders on the ground, he recommended to the British War Cabinet that the peninsula be evacuated as little progress could be made without major reinforcements.
NZ Defence Force
tweets: Lovely to have their Royal Highnesses Prince Charles and Prince Harry at the NZ Chunuk Bair Anzac service #Anzac100 #gallipoli2015
John Key
Prime Minister of New Zealand
tweets: "For New Zealanders, nowhere in Gallipoli is more special than here on Chunuk Bair." #ANZAC100
Clarence House
tweets: The final service Their Royal Highnesses are attending for #Anzac100 is at Chunuk Bair, the New Zealand memorial
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Turkish ambassador
Abdurrahman Bilgic, the Turkish ambassador in the UK, speaks during a wreath-laying ceremony at St Paul's Cathedral earlier.
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Scottish ceremony
Nicola Sturgeon, the First Minister of Scotland, lays a wreath at a special ceremony to mark the Gallipoli centenary at Edinburgh Castle.
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New Zealanders at Chunuk Bair
Chunuk Bair bore witness to a courageous stand by New Zealand forces during the offensive of August 1915.
They were ordered to capture and hold the strategic summit, which they did during a desperate struggle. They were relieved by British troops and the summit was lost shortly after during a determined Turkish counter-attack.
It was the closest to a breakthrough the Allies achieved in the whole campaign.
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Prince Harry and Prince Charles are attending their final service as part of the Gallipoli commemorations. It is at Chunuk Bair, the New Zealand memorial.
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Temporary truce
Fierce attacks and counter attacks in the first few months of the Gallipoli campaign left soldiers' corpses exposed to the elements in no man's land.
On 24 May, the Allies agreed to a one-day truce to allow both sides to bury their dead, as the summer heat had caused the bodies to rot, causing an unbearable smell.
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The Allied force in numbers
The Allied forces were commanded by Briton Sir Ian Hamilton. Most of his overall force of 75,000 men were on the Peninsula by mid-May.
In August they were joined by 60,000 more men at Suvla Bay. In December 1915 to January 1916, 105,000 men were evacuated from the Peninsula.
45,000 Allied soldiers and 85,000 Turkish soldiers died between April 1915 and January 1916.
Daniel Boettcher
BBC News correspondent
Among those watching the ceremony were 10-year-old Edward Jackson, wearing the medals of his great grandfather, Commander Arthur Mallet, who served in the Royal Navy and was injured during the campaign. Near the Cenotaph, artist Nadir Imamoglu, born in Turkey but living in the UK for 40 years, has set up a sculpture based on a larger one he has created at the National Memorial Arboretum in Staffordshire. It is made of young oak trees- to reflect the ages of the men fighting at Gallipoli - the bare branches reaching into the sky. The sculptor explains this represents the arms of those injured in battle reaching out for help.
Daniel Boettcher
BBC News
Before the wreath-laying ceremony those gathering to take part heard music led by the massed bands - pieces drawn from some of the countries that took part in the Gallipoli campaign. Those waiting along Whitehall to lay their wreaths listened in silence - service personnel, veterans of more recent conflicts, members of military associations including the Gallipoli Association. Also present were descendants of those who fought in the campaign.
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The Cenotaph ceremony is concluding with a march past.
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Turkish pride
The defending Turkish troops were driven by a grim determination at Gallipoli. The 19th division were led by Lt Col Mustafa Kemal, who later founded modern Turkey.
He told his officers: "I don't order you to attack - I order you to die. In the time which passes until we die, other troops and commanders can take our place."
At Anzac, Kemal's forces held on to the high ground and stopped the Australians and New Zealanders from advancing. They also stopped Allied forces advancing north of Krithia in Helles.
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Before poppies
Before the poppy or the other symbols of remembrance that we know today came into being, people started to mark the absence of those at the front.
From 1916, street shrines began to appear. A year later, the Imperial War Museum was founded to record the conflict for future generations. The Imperial War Graves Commission (IWGC) was established to record the deaths and mark the graves of those who had fallen.
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Here is Michael Toohey, wearing his fallen relative's medals.
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Michael Toohey, 22, was among the young people to give a reading at the Cenotaph. His great-great uncle died on the first day of the Gallipoli campaign and Michael was wearing his medals.
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Leaders
In addition to the Prime Minister David Cameron, Labour leader Ed Miliband, Deputy Prime Minister Nick Clegg and UKIP leader Nigel Farage were also present at the Cenotaph ceremony.
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Shell shock
Soldiers experienced severe psychological strain at Gallipoli, and many suffered from what we now know to be depression, anxiety and post-traumatic stress disorder.
Those with symptoms were said to have 'shell shock' as doctors first thought the conditions were caused by an invisible force from exploding shells.
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Poppies to remember
Poppies have been laid to remember those who were killed at Gallipoli.
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The Queen. Duke of Edinburgh and the Duke of Cambridge at the Cenotaph
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The scene at the Cenotaph in Whitehall, London.
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God Save Our Queen is sung at the Cenotaph.
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Wreath laying and readings have been followed by band music.
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The Turkish national anthem rings out at the Cenotaph.
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Guards stand near the Cenotaph as the ceremony's events continue.
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Following a prayer read by 11-year-old New Zealander, Kathryn Cooper, the New Zealand national anthem is played at the Cenotaph.
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Boy soldiers
In total, about 50,000 Australians were sent to Gallipoli. The youngest, James Martin, was only 14 years old. People were supposed to be 18 to enlist in Australia and 19 in Britain, but tens of thousands of underage soldiers managed to join up.
James died from typhoid fever in October 1915 and was buried at sea.
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The Australian national anthem is being played and sung at the Cenotaph.
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The Gallipoli Memorial, which commemorates all those who took part in the campaign, was erected by the Gallipoli Association and unveiled in November 1995 by Prince Philip in the presence of eight surviving veterans.
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Before the Cenotaph ceremony, the Duke of Edinburgh led the annual wreath-laying ceremony at the Gallipoli Memorial in the crypt of St Paul's Cathedral.
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A lasting memorial
The Cenotaph was designed and built by Edwin Lutyens to mark Peace Day events in July 1919. It was only supposed to be a temporary structure and was built from wood and plaster.
When unveiled in November 1919, the public spontaneously covered it in floral wreaths. It was so popular it was rebuilt a year later in Portland Stone to become a permanent and lasting memorial.
Peter Hunt
BBC Royal correspondent
tweets: Prince William is at the Cenotaph Gallipoli commemorations. Not yet at the private Lindo Wing. #RoyalBaby
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The Australian, New Zealand and British military are all represented at the Cenotaph ceremony.
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David Cameron followed the Queen in laying the wreath at the memorial.
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The Queen bows after laying the wreath.
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The Queen laying her wreath at the Cenotaph.
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Prime Minister David Cameron places the second wreath, followed by the representatives from Australia, New Zealand and Turkey.
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The Queen steps forward to lay the first wreath at the foot of the Cenotaph
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The Last Post sounds to mark the end of the silence
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The Queen is accompanied by the Duke of Edinburgh and Prince William
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The chimes of Big Ben mark the start of a two-minutes' silence.
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The Queen will lay the first wreath.
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British politicians are joined by Australia's attorney general and the speaker of New Zealand's House of Representatives as wreath bearers.
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Choristers at the Cenotaph
Choristers from Chelmsford have been singing at the Cenotaph.
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The wreath bearers emerge at the Cenotaph.
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Cenotaph service
The ceremony to mark the centenary of Gallipoli has started at the Cenotaph in London.
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Losing their bearings
The Allies had been issued with standard 1:40,000 scale maps for the attack. However, these failed to show important details of the hilly terrain. The heights given for many of the hills were also incorrect.
A group of New Zealanders heading from Plugge's Plateau to Russell's Top had to make an hour's detour into a valley because the map didn't show the two were joined by an impassable ridge.
By August the maps were gradually replaced by more accurate 1:20,000 maps redrawn from captured Turkish maps.
Clarence House
Prince Harry and Prince Charles in Gallipoli
tweets: TRH visit the Nek Cemetery, where many Australians who fell in the charge of the 3rd Light Horse Brigade are buried
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The first days
Over three days British troops consolidated their position from the landing beaches to form a line across the tip of the Gallipoli Peninsula. However, they then failed to take the village of Krithia on the slopes of Achi Baba.
Achi Baba was their first-day objective but they failed to hold it during the campaign.
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Landing at Helles and Kum Kale
At Cape Helles, 3,000 Tommies landed at Y Beach, and some 15,000 landed at W, X, V and S beaches. Their objective for the first day was to secure Achi Baba, a ridge about a mile inland.
Around 3,000 French troops landed at Kum Kale on the Asiatic shore. This was a feint designed to confuse the enemy and draw off the long-range guns. A few days later the French joined the British at Helles.
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A nurse at Gallipoli
Sister Kathleen "Kitty" Mann was serving on the HMAT Ulysses and kept a diary on board:
"We lost a patient this morning after he had had two operations, poor boy, it was sad, only 24hrs, and he had been through so much (gas gangrene); it was horribly sudden.
"I witnessed a burial at sea for the first time that day. It was held on the end deck after lunch, the body being placed on a slanting board, covered with a union jack. The burial service was read by the Captain, there being no Padre; others attending were the OC Troops and some of the medical staff. It was most impressive and quite reverently done."
Nurse Kathleen Mann, 23 August, 1915. Extracts displayed at Hospital + Troop Ships exhibition on board HQS Wellington.
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Modern medicine
"To say that since writing last we have been through a literal hell is putting things very mildly."
Major Vivien Benjafield, of the Australian Army Medical Corps, IWM
Surgeons and nurses were severely tested by the ferocity of modern warfare, but the conflict also led to medical innovations.
Ed Miliband
Labour leader
tweets: Soldiers came from across the globe to stand with Britain in our nation's hour of need, and they must never be forgotten.
Ed Miliband
Labour leader
tweets: The centenary of Gallipoli is a moment for Britain to remember those who died in one of the First World War's most traumatic chapters.
Order of the day
The Lone Pine ceremony is concluding with the ceremonial laying of wreaths. British Foreign Secretary Philip Hammond is among those laying flowers at the memorial site. Shortly Turkey is to hold a service at the Turkish 57th Regiment Memorial on the peninsula, followed by a New Zealand service at Chunuk Bair, scene of a bloody battle for the imposing summit. At 1100 BST, there is a further service at the Cenotaph in central London, followed by a 1300 BST service at Westminster Abbey.
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Landing at Anzac
Some 12,000 men landed at Anzac (Z beach) on 25 April. Their objective for the first day was to secure the third ridge, later called Gun ridge, about a mile inland.
However, after the initial surprise, the well-prepared Turkish defences managed to contain the Allied troops. They were led by Mustafa Kemal who would later become the founding father of modern Turkey.
Lone Pine service
Australian PM Tony Abbott takes to the podium and pays his tribute: "To us they are Anzacs, but in their day they were fathers, sons, parents, children, cousins and mates just as you are now. You walk among their headstones, you read the inscriptions, you hear the epitaphs and you hear their families speak - in these inscriptions and in these epitaphs we hear the echoes of our country a century ago." You can watch the service by clicking on the Live Coverage tab at the top of this page.
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Prince Harry's address
Prince Harry has begun speaking at Lone Pine: "In this quiet place it is difficult to imagine the carnage, the desperation of the fighting that took place here. But it was in this spot that many acts of valour took place, and despite the number of Victoria Crosses awarded for the fighting here, most of those acts went unrecognised. Great valour was a common virtue."
'One of bloodiest battles'
Air Chief Marshal Mark Binskin describes Lone Pine as "one of the bloodiest battles in Australia's history". He tells the congregation: "The Gallipoli campaign exacted a heavy toll that left an indelible scar on our nation." Of the ordinary men who "found extraordinary determination" in the name of duty, he says "we honour them, and the actions that inspired the Anzac spirit".
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Lone Pine, August 1915
By summer 1915 there was a stalemate at Gallipoli. In August new offensives and landings were launched along the peninsula to try and break it.
At Lone Pine, Anzac troops fought a fierce three-day battle to take the pine-log covered trenches here. They sustained 2,300 casualties and won 7 Victoria Crosses in the action.
The New Zealanders briefly occupied the strategic high point at Chunuk Bair before misdirected friendly artillery fire and a Turkish counter-attack forced off the British and Gurkhas who had relieved them.
Veterans honoured
There is a heartfelt round of applause at Lone Pine as all veterans present at the ceremony are invited to stand. The emotion of the occasion is clear on the faces of some of the 8,000 proud Australians attending.
St Paul's remembrance
As the Australian memorial service gets under way in Gallipoli, the Duke of Edinburgh, patron of the Gallipoli Association, is joining the congregation at St Paul's Cathedral for a service of remembrance in London.
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Light moment ahead of service
Australian PM Tony Abbott and Prince Charles have chatted with members of the crowd gathered at Lone Pine ahead of the Australian memorial service. Both men had an early start today, addressing at a pre-dawn ceremony. Prince Charles spoke movingly about soldiers who were "tormented by the thought of their comrades being left behind" and that their graves would remain unvisited.
Watch: Lone Pine service
The Australian Service is about to get under way at Lone Pine on the Gallipoli peninsula. You can watch live video from the ceremony by clicking on the Live Coverage tab at the top of this page.
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Treating the wounded
Nurses treated patients on hospital ships such as the converted HMHS Devanha off the coast of Gallipoli under risk of artillery fire.
Hospital ships were merchant vessels crewed by merchant seafarers, who were civilians.
They ferried the injured to hospitals on islands such as Lemnos and Malta as well as Egypt and England. If they died en route they would be buried at sea.
Do Australians risk Anzac fatigue?
Wendy Frew
Australia editor, BBC News Online
The Australian government is spending A$145m ($113m, £76m) on Anzac commemorations including building an Australian Remembrance Trail on the Western Front, refurbishing the Australian War Memorial and building a new Australian War Memorial in New Zealand. That compares with the £50m being spent by the UK government on World War One commemorations. Some are asking whether Australians risk Anzac fatigue.
Nightclub 'interrupts service'
The Sydney Morning Herald website is leading with the story of how Saturday's dawn services marking the centenary of Anzac Day were interrupted by music from a nearby nightclub several times. The owners of the club have apologised and blamed unauthorised sound testing for an event later in the day.
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Pictures from London service
More pictures have been coming in from the Anzac Day Dawn Service at Wellington Arch in London. Princess Anne was among the dignitaries attending.
Get involved
Email talkingpoint@bbc.co.uk
William in London writes: I will remember that my maternal grandfather, William Wright, served at Gallipoli in the Sherwood Rangers Yeomanry - he survived and was posted to Palestine. Two very important future leaders also served at Gallipoli: Prime Minister Clement Attlee and Field Marshal the Viscount Slim.
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Extreme weather
Soldiers experienced extreme weather in Gallipoli, with a heatwave in summer and a freezing winter.
"I woke up to the find the whole country white. It looks beautiful and covers over so many things which are not."
Private Ronald McInnis, 26th Battalion, November 2015, AWM
But many men were under-prepared for the cold conditions. A blizzard in November caused 160,000 cases of frostbite and 280 men froze to death.
Lone Pine service
The BBC's Lucy Hockings is at Lone Pine cemetery which she said is filling with Australians ahead of a service of remembrance in a few hours time. Many of those gathering were up to attend pre-dawn services on the Gallipoli peninsula. In August 1915, the area was the scene of one of the bloodiest battles in Australia's history as the Anzacs pitched themselves against a series of formidable entrenched Turkish positions.
Watch: Drone video
For an overview of the Gallipoli peninsula and the battle sites, watch this film made using a drone.
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U-boat threat
Allied shipping was terrorised by German U-boats throughout World War One. At Gallipoli, the U-21 sank two British battleships in May 1915 - HMS Triumph and HMS Majestic, with the loss of nearly 200 men.
While the U-21 survived the war, most submarines didn't. They were effectively death traps.
London services
A dawn service attended by the Princess Royal is taking place at Wellington Arch in Hyde Park Corner, London. It's an annual event but larger crowds were expected this year.
At 11:00 BST there will be a wreath-laying ceremony and parade at the Cenotaph on Whitehall attended by the Queen, Prince Philip and the Duke of Cambridge, and at 13:00 BST a service of commemoration at Westminster Abbey.
Forgotten Indigenous soldiers
During World War One, Australia's Defence Act 1903 excluded people who were not substantially of European descent from enlisting, but some got round the rules.
Saffron Howden for BBC News tells some of the stories of Indigenous Australian soldiers.
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Anzac Spirit
Amid the slaughter and sacrifice at Gallipoli, stories emerged of resilience and mateship in the heat of battle. Labelled by journalist Charles Bean as the 'Anzac Spirit' it fulfilled a much-needed craving in Australia and New Zealand for a national identity.
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Lucy Hockings
BBC News correspondent
tweets: 100 years later, bullets found on the beach at #Anzac Cove. #Gallipoli100
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Dawn attack
The Anzac Corps were the first Allied troops to land at 4.30am on 25 April, 1915. They were towed in chains of small vessels behind steam boats, before they rowed the final 50m (164ft) to shore.
The first troops landed unopposed but on the wrong stretch of beach, now known as Anzac Cove. They had intended to land a mile further south, which didn't have such a steep incline. Soldiers used their bayonets to start scrambling up the hill.
Dawn ceremony concludes
The dawn ceremony is now over. Australians will soon move off to Lone Pine for a service starting in four hours while New Zealanders remember their dead at the other upper level battleground of Chanuk Bair.
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As it's almost completely light, the Last Post is performed. A minute's silence will follow.
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A prayer of remembrance and the Lord's Prayer were read before wreaths were laid.
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Prince Charles read the words of Lieutenant Ken Millar and Company Quartermaster Sergeant Benjamin Leane, written during the campaign.
'I died loving you'
Wendy Frew
Australia editor, BBC News Online
Like many Australians, I have ancestors who served in World War One. The stories of their military service are well known by my relatives and their diaries, letters and medals are precious family relics.
One of those letters — written by my great-great uncle, Benjamin Bennett Leane — was read by Prince Charles to the crowd gathered in the cold dawn at Anzac Cove.
Two days before the fateful morning when the Anzacs landed on the shores of Gallipoli, Benjamin, then a captain in the Australian army, wrote a letter to his young wife that he feared would be his last:
"Know that I died loving you with my whole heart and soul, dearest wife that a man ever had. Kiss little Gwen and our new baby, who perhaps I may never see, and never let them forget Daddy."
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The Allies had reached a stalemate on the Western Front by September 1914. A month later the Ottoman Empire formally joined the Central Powers, led by Germany, when it bombed Russian seaports.
Winston Churchill, then First Lord of the Admiralty, planned to knock the Ottomans out of the war by attacking the capital Constantinople.
The navy first had to force open a route along the Dardanelles by the Gallipoli peninsula. This was a total disaster. A larger land assault was devised in its stead.
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Australian Prime Minister Tony Abbott tells the thousands gathered at Anzac Cove on Turkey's Gallipoli peninsula, the men who left from "every rung of the ladder" became "the founding heroes of our modern Australia".
'Wipe away your tears'
A quotation by Mustafa Kemal Ataturk - the founder of the Republic of Turkey after the fall of the Ottoman Empire - is read.
"You, the mothers who sent their sons from faraway countries wipe away your tears; your sons are now lying in our bosom and are in peace.
"After having lost their lives on this land they have become our sons as well."
John Key address
John Key, prime minister of New Zealand, is making an address.
He says: "Time and perspective have cast the Gallipoli campaign in a different light but 100 years ago both sides were doing what they believed was right and necessary."
He salutes the bravery of all who have fought on the peninsula.
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Princes Charles and Harry are among a large number of international dignitaries and thousands of members of the public gathered in the dark in silence.
Call to Gathering
The dawn service is due to begin shortly. We just heard a Maori Call to Gathering performed by women of the New Zealand Defence Force. You can watch the service on BBC News.
Roll of honour
The names and epitaphs of the Australian and New Zealand soldiers who died at Gallipoli are now being shown on a big screen.
Ceremony begins
The Spirit of Place - preceding the dawn service - has begun with a didgeridoo performance and a soliloquy about the landing.
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What was Gallipoli?
The Gallipoli Campaign was an ambitious military operation in World War One to knock the Ottoman Empire out of the war.
The British and French-led force planned to seize the capital Constantinople (now Istanbul) by launching a land and sea assault from the Turkish Gallipoli peninsula.
They planned to advance 200 miles (320km) north-east to the capital but only succeeded in establishing a tiny foothold at Gallipoli.
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Among the dawn memorial events that have already taken place, images of soldiers were projected onto a building near the Cenotaph war memorial in Sydney.
Prime ministers unite
tweets: Anzac spirit alive and well - on the bus to Gallipoli for the dawn service with @TonyAbbottMHR.
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Thousands of Australians and New Zealanders have waited overnight for the dawn service at the Anzac Commemorative Site in Gallipoli. To attend they had to enter a ballot.
What's planned?
In the next few hours a memorial dawn service will take place near to the site of the landings in Turkey.
Australia and New Zealand's prime ministers, Prince Charles and Prince Harry and 10,000 people are expected to attend.
Afterwards, Australians will walk to Lone Pine, the site of a battle where the country suffered more than 2,000 casualties.
Meanwhile, New Zealanders will attend a memorial at Chunuk Bair, a summit which was the scene of heavy fighting.
A dawn service will be held in London and a march past later at the Cenotaph.
Australia and New Zealand events
Australia and New Zealand have marked the centenary of dawn landings at Gallipoli with memorial services.
Events in Canberra, Sydney, Brisbane and Melbourne were attended by thousands of people, as were similar events in New Zealand including a big ceremony in Wellington.
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About 131,000 troops - 45,000 Allied forces and 86,000 from Turkey - died at Gallipoli.
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Welcome to BBC News's live page marking the 100th anniversary of the Gallipoli campaign.
A series of events will be taking place on the Turkish peninsula on Saturday to commemorate one of the bloodiest campaigns of World War One.