Torn in two: Yemen divided

Yemen is broken. The country once dubbed by the Romans as "Arabia Felix" - "Fortunate Arabia" - because of its lush valleys and rich agriculture has been torn apart by war.

The UN estimates that close to 6,000 people have been killed since a Saudi-led nine-nation coalition began air strikes in March 2015, hoping to defeat the Houthi rebels who had taken over half the country.

Already the poorest country in the Arab world, with dwindling oil and water reserves, Yemen is now facing catastrophe. Its basic infrastructure is shattered, its economy is grinding to a halt, at least 80% of the population is dependent on food aid.

Its land is divided between Houthi rebels, forces loyal to the former president, forces loyal to the current president, Gulf Arab armies and rival jihadists from both al-Qaeda and so-called Islamic State (IS).

Peace talks in Switzerland opened in December but if they fail to produce results when they resume in January then Yemen's largely unseen war could last well into 2016 and beyond.

What went wrong?

In 2011, Yemen experienced the Arab Spring protests, along with Egypt, Tunisia, Bahrain, Libya and Syria.

Like much of the Arab world, Yemenis came out onto the streets to demand an end to corruption and a total disrespect for human rights

Worried that the protests could spill out of control or even beyond its borders, Yemen's Gulf Arab neighbours brokered a deal that saw longstanding President Ali Abdullah Saleh deposed and replaced by President Abdrabbuh Mansour Hadi.

They underestimated the former president. Instead of slipping off gracefully into retirement, Mr Saleh remained in Yemen, conspiring to ruin the new president's chances of success.

Saleh had ruled North Yemen since 1978 and a united Yemen since 1990, so was able to retain the loyalty of much of the army and police

In 2014, Mr Saleh threw his support behind a rebellion by the Iranian-backed Houthi rebels, enabling them to march almost unopposed into the capital, Sanaa.

By January 2015, the UN-recognised President Hadi had lost power completely and he fled into exile in Saudi Arabia where he remains today. By March 2015, the Houthis had taken over the whole of western Yemen, where the bulk of the population are concentrated.

The Saudis and their Gulf Arab allies saw this as an Iranian takeover, fearing that Iran was about to seize control of Aden port and the strategic entrance to the Red Sea, through which thousands of ships pass each year.

For the Saudis, this was a red line and they decided to act. In March, they began a massive campaign of air strikes, targeting both the Houthi rebels and their backers, the units loyal to Mr Saleh.

The Saudis expected their overwhelming firepower to quickly drive the Houthis towards the negotiating table, and that they would sue for peace. Yet, nine months later the Houthis remain firmly embedded in the capital and much of the north.

Yemen now effectively has two capitals - Sanaa and Aden - and the Saudi-led coalition is bogged down in an indecisive war where neither side is emerging as a clear winner.

The human cost

The toll on Yemen's population and infrastructure has been horrific. According to human rights groups both sides have committed abuses, some of which may amount to war crimes.

More than 2,500 civilians are reported to have been killed, most by air strikes. The Saudi-led coalition stands accused of using at least four types of cluster bombs and dropping bombs on civilian homes, hospitals, factories and bottling plants.

Saudi-led air strikes have had a devastating effect

There has been widespread disruption of water supplies - aid agencies have warned of the growing risk of malnutrition and disease

More than 2.5 million people have been displaced internally

Saudi Arabia insists it only attacks carefully chosen military targets but there have been numerous accounts from Yemenis on the ground saying residential areas have been attacked, far from any Houthi positions.

Human rights groups have called for a boycott of Western arms sales to Saudi Arabia since its air force uses US- and UK-made planes and missiles, while US tankers resupply those aircraft and US intelligence advisers work alongside the Saudis in their operations centre.

The Houthi rebels are accused of shelling residential areas indiscriminately, of laying unmarked mines and of imprisoning members of the population without charge. Food distribution has been hampered by the fighting and by a partial blockade of Yemen's ports and aid agencies warn of the growing risk of malnutrition and disease if the war continues much longer.

The strategic picture

Some see the Yemen conflict as a sectarian proxy war between the two big regional rivals in the Middle East: Saudi Arabia and Iran.

Saudi Arabia is a Sunni-majority country where the Shia population in the east complain of marginalisation and discrimination. Iran is a Shia-majority country. The two are vying for control and influence over a rapidly-changing map of the Middle East.

Until the US-led invasion of Iraq in 2003 that large, oil-rich country was ruled by Sunnis under President Saddam Hussein. Gulf Arab rulers did not much care for him but they saw Iraq as a useful bulwark against Iran and its efforts to export its Islamic Revolution.

But today Iraq is ruled by Shias and has very close links with Iran. Syria, riven by civil war, has a nominally Shia president supported by Iran, while next door in Lebanon the most powerful militia is Hezbollah, also supported by Iran.

Armed tribesmen loyal to Yemen's Saudi-backed government

So the Saudis are feeling a certain paranoia, fearing a "Shia crescent" that extends all the way from Afghanistan westwards to the Mediterranean. The prospect, in their eyes, of Yemen forming part of this Shia sphere of influence was simply too much for them, hence their commitment to a Yemen war with no apparent end in sight.

Saudi Arabia, the UAE and Bahrain all now appear more interested in what happens in Yemen than what happens in Syria.

In practice, this has translated into a scaling back of Gulf Arab participation in the US-led air campaign against IS in Syria and Iraq.

Saudi Arabia, UAE and Bahrain are fully committed militarily in Yemen and analysts question whether these countries can focus their full attention on two full scale conflicts simultaneously.

Expeditionary warfare

The new, aggressive and adventurist stance of the Saudi ruling clique has surprised many people. Despite the billions of petrodollars they have spent on arms purchases over the years, the Saudis have not been a martial nation since the country's tribes united back in 1932.

When Iraq's late President Saddam Hussein invaded Kuwait in 1990, some Saudi princes even suggested a deal that would buy him off and let him keep part of Kuwait. Traditionally, the Saudis have preferred to conduct diplomacy by quiet negotiation and compromise, backed by cash, rather than seeking confrontation.

But that changed after January 2015, when the late King Abdullah was succeeded by King Salman, who granted extraordinary power to his young and untested son, the 29-year-old Prince Mohammed bin Salman. As possibly the youngest defence minister in the world, he was given the green light to lead the war against the Houthis in Yemen.

Prince Mohammed bin Salman has overseen the military operation in Yemen

Today, Saudi troops are on the ground there, but under the same banner of the Saudi-led coalition so too are Emiratis from the UAE, Bahrainis and, reportedly Egyptians, Sudanese and even Colombian mercenaries.

In September, a single missile attack on a coalition base killed 46 Emirati soldiers and several Saudis and Bahrainis.

The UAE has some experience of expeditionary warfare (sending troops overseas to fight), after serving in Kosovo and Afghanistan, but for the Saudis the war in Yemen is a new and risky venture.

Any deal that leaves the Houthi rebels in control of Sanaa and the surrounding area will be perceived as a failure for the Saudis and their coalition, something that could have negative consequences for the young defence minister.

But reports from Yemen suggest that splits have emerged between the Houthi rebels and their Saleh backers. There are signs that some Houthi leaders want to bring this war to a swift end, while others want to fight on.

So, as ever, the situation in Yemen is complicated. Ceasefires come and go, peace talks are convened then break up, more and more countries are getting drawn into the morass and with no clear winner, it is Yemen's increasingly beleaguered population that is emerging as the losers in this war.