Death tollpublished at 19:00 BST 1 July 2016
An accurate death toll over the course of the Battle of the Somme is an impossibility. But it is thought that as many as a million men were killed in those 20 weeks.
Image source, Getty ImagesSummary
Battle of the Somme - as it happened
Almost 20,000 British soldiers were killed on the opening day of the battle
2,069 men from the 36th Ulster Division were killed at the Somme on 1 July 1916
All times are +1 hour BST
Picture: Attack on Thiepval, Getty Images
Death tollpublished at 19:00 BST 1 July 2016
Image source, Getty ImagesHindenburg linepublished at 18:40 BST 1 July 2016
In early 1917, the Germans fell back to the safety of the Hindenburg line - negating all the gains for which the Allies had paid such a high price.
Image source, Getty ImagesImage caption, The Hindenburg line
What was learned from the Somme?published at 18:20 BST 1 July 2016
The Battle of the Somme saw British improvements in trench warfare. The creeping barrage was improved; tanks were used for the first time; intelligence got better.
Image source, Getty ImagesA battle that lasted 141 dayspublished at 18:11 BST 1 July 2016
The Battle of the Somme would continue for almost five months. The British lines moved forward by about 4.5 miles (7km).
Image source, Getty ImagesThe bloodiest daypublished at 17:57 BST 1 July 2016
As dusk descends on the Somme, it becomes apparent that the British army has suffered its bloodiest day. In all, the first day saw 57,470 British casualties - 19,240 dead. In comparison the German army had around 6,000 casualties.
Image source, Getty ImagesCounting the Ulstermen's deadpublished at 17:50 BST 1 July 2016
The 36th Ulster Division finishes the first day of the Battle of the Somme right back where they started. But with more than 5,000 casualties - around 2,069 of them lying dead.
Image source, Getty ImagesHorrific casualty ratepublished at 17:37 BST 1 July 2016
The battle rages on into the evening. The first day is yet not over but the casualties count is rising at an alarming rate.
Image source, Getty imagesBack to British linespublished at 17:22 BST 1 July 2016
On the way back towards the British front lines, they meet the reinforcements they were hoping for about seven hours earlier.
Image source, Getty ImagesUlstermen retreatpublished at 17:06 BST 1 July 2016
The Germans are exhausted and the 36th manages its retreat in an orderly fashion.
Image source, Getty ImagesUlstermen forced back to German front line trenchpublished at 16:55 BST 1 July 2016
The Ulster men fall back to the initial German front line. They brace themselves for an onslaught.
Image source, Getty ImagesGiving up the Schawbenpublished at 16:38 BST 1 July 2016
The order is given to relinquish the Schawben Redoubt.
Image source, Getty ImagesThe defence of the Schawben Redoubt is becoming desperatepublished at 16:24 BST 1 July 2016
Fewer men and fewer bullets means the Ulster Division's defence is becoming increasingly desperate. The Germans just keep coming.
Image source, Getty ImagesUlstermen being attacked on three sidespublished at 16:09 BST 1 July 2016
Another determined German counter-attack. It's coming from three sides.
Image source, Getty ImagesThe Ulster Division are managing to hold the Schwabenpublished at 15:54 BST 1 July 2016
So far, the Germans haven't succeeded in breaking through the Ulstermen. But it's only a matter of time.
Image source, Getty ImagesNo reinforcementspublished at 15:39 BST 1 July 2016
With scant possibility of reinforcements any time soon, the 36th Division have to attempt to hold on until dark.
Image source, Getty ImagesThe Ulster Division faces a German backlashpublished at 15:24 BST 1 July 2016
The German counter-attacks just keep coming.
Image source, Getty ImagesGerman attack on Ulster Division is fiercepublished at 15:14 BST 1 July 2016
The counter attack from the Germans is fierce coming from the direction of the village of Grandcourt.
Image source, Getty ImagesThe Ulstermen are on their ownpublished at 15:00 BST 1 July 2016
Communication with the Ulstermen through No Man's Land is nigh on impossible.
The Ulster Division has nowhere to gopublished at 14:44 BST 1 July 2016
The men from the 36th who are at Schwaben are effectively cut off from their nearest comrades. No-Man's Land isn't an option for the Ulster Division at the minute - the German machine gun fire from Thiepval is almost constant.
Image source, Getty ImagesThe counter attacks beginpublished at 14:30 BST 1 July 2016
The Germans want the Schwaben Redoubt back and start their counter attacks to take it.
Image source, Getty Images