A week ago, a coalition of 10 countries led by Saudi Arabia began to bomb Yemen. The unrest involves several different actors and constantly changing allegiances. Here is IRIN's guide to the major players in the conflict and a reading list to help unravel the complex reasons behind it:
Ali Abdullah Saleh ruled Yemen as president for 33 years until 2011, when he agreed to leave office after 10 months of violence following Arab Spring-inspired protests. The terms of his resignation – brokered by the Gulf Co-operation Council (GCC) of which Saudi Arabia is a leading member – gave Saleh full immunity against prosecution and he has continued to manoeuvre behind the scenes. During the 2000s, his government fought a five-year war with the Houthis, who opposed Saleh’s close ties with Saudi Arabia and his support for US-led counter-terrorism operations. However, in recent months, the former president, who still commands loyalty within the Yemeni military, has switched sides and now backs the Houthis against the Saudi-led assault.
Abd Rabbu Mansour Hadi is the internationally-recognised president of Yemen. He was Saleh’s deputy and took over the top job in 2012 after winning an election in which he was the sole candidate. Hadi attempted to clean up the widespread corruption and reform the country’s military, but his performance received mixed reviews as he struggled to repair the weak economy. In January, four months after the Houthi advance on the capital Sana'a, the presidential palace was seized and Hadi was placed under house arrest. He resigned, but less than a month later, after escaping custody and fleeing south to the port city of Aden, he withdrew his resignation and sought refuge in Saudi Arabia.
The Houthis - who refer to themselves as Ansar Allah (“supporters or partisans of Allah”) - belong to the Zaydi sect of Shia Islam followed by around a third of the Yemeni population. The Houthis are often described as being backed by Shia-majority Iran, but others say they are primarily a local group and argue that to call them proxies of Iran is inaccurate. Zaydis ruled the northern part of Yemen for centuries until 1962, and in the early 2000s the Houthis formed a rebel group to claim autonomy for the northern Saada region, fighting against the government of Saleh and his then key ally, Saudi Arabia. After seizing the capital Sana'a in September – and putting President Hadi under house arrest in January - the group began to move south towards Aden, into which they advanced in early April.
Saudi Arabia, which has been propping up Yemen’s economy for years but cut aid after the Houthi seizure of Sana'a, launched airstrikes in March - under the tag “Operation Decisive Storm” - to stop the advance of the Houthi rebels, whom it regards as a proxy for its regional nemesis Iran. The airstrikes are being backed by a number of countries, including the United Arab Emirates (UAE), Kuwait, Bahrain and Egypt, who are all calling for the Houthis to give up seized territory and allow Hadi to be reinstated as president. Yemeni government officials loyal to Hadi have called on Saudi Arabia to send in ground troops.
Iran is widely reported to be pulling the strings of the Houthis in their fight against Saudi-backed Hadi, but, so far, beyond media reports about weapons and money being set to the rebel group, there is little evidence to support these claims. However, Tehran has celebrated Houthi advances within Yemen and loudly criticised the Saudi-led military action.
Al-Qaeda in the Arabian Peninsula (AQAP) – or Ansar al-Sharia as they call themselves – has been involved in a number of terror strikes around the world - including the Charlie Hebdo attack in Paris - and several kidnappings and killings within Yemen in recent years. The United States has been using drones to target the Sunni Muslim extremist group. President Barack Obama once famously referred to US operations in Yemen as a "model" for fighting terrorism. But the indiscriminate nature of the drone strikes and the high number of civilian casualties has upset Yemenis and helped AQAP win some local sympathy.
Want to know more?
IRIN recommends the following reading and listening:
A mix of analysis and on-the-ground articles from one of the world’s most under-reported countries seen through our unique humanitarian and local lens.
Adam Baron, who until recently worked as a journalist in Yemen, is an excellent source of clear analysis on this complicated country.
Listen to a first-hand and nuanced account of the Yemen from journalist Safa al-Ahmad, who has just returned from making a BBC Arabic documentary there.
More from Adam Baron, this time via a podcast from Middle East Week hosted by Karl Morand.
The Guardian’s Middle East Editor Ian Black helps unpick the complex web that is Yemen.
The Bureau of Investigative Journalism has detailed reportage on the impact of drone strikes in Yemen.
A round-up of commentary on Yemen from a leading global think-tank
Experts from the respected Brookings Institution think-tank express their views on the developing situation in Yemen and what it might mean for wider political stability.