Conflict sparked by failed power transition

Sheik Heikel Khalid Bafana, a 48-year-old Singaporean, was recently detained under the Internal Security Act for taking up arms and fighting alongside a faction in the Yemen civil war.

In a statement last Wednesday, the Internal Security Department said Heikel had also acted as a broker between this faction and the foreign power, which was not named. Here, ST explains what the Yemen civil war is about.

The civil war started in 2014 between Houthi rebels and government forces. But seeds of the conflict were sown in the 2011 Arab Spring when mass demonstrations and a near-assassination of long-time authoritarian President Ali Abdullah Saleh forced him to step down and hand over power to his vice-president Abed Rabbo Mansour Hadi. The political transition a year later, overseen by the United Nations, failed to bring stability to the country.

In 2014, the Houthis - an anti-government rebel group which champions the Zaidi Shi'ite minority - launched a rebellion after forging an unlikely alliance with former president Ali Abdullah, who had wanted to regain power.

The Houthis had their northern strongholds in and around Saada province in late 2014, before moving south and overrunning nearly the entire country, including the capital Sana'a. A power-sharing deal between the Houthis and the government brokered by the UN was ignored. Mr Abed Rabbo fled to Saudi Arabia in March 2015.

At his request, Saudi Crown Prince Mohammad bin Salman organised a coalition that involved eight other Sunni Arab states, including the United Arab Emirates, to intervene in Yemen. The coalition - together with local forces - launched air and sea strikes to finish off the Houthis quickly and restore Mr Abed Rabbo to power. Saudi Arabia fears the Houthis would become yet another Shi'ite proxy of Iran.

The Saudi-led coalition is backed by the US, Britain and France, which not only supplied weapons but also provided logistical and intelligence support.

The Houthis were pushed back but not dislodged from territories they seized in the north, including Sana'a. With Iran's help, they launched missile and drone attacks on Saudi Arabia, some of which hit prime targets like oil fields. In 2017, the Saudi-led coalition tightened its blockade of Yemen. But it only worsened Yemen's humanitarian crisis. The alliance between the Houthis and Mr Ali Abdullah fell apart in November 2017. Mr Ali Abdullah died in a clash one month later.

In July 2019, the UAE withdrew from the war. The Southern Transitional Council (STC), a UAE-aligned separatist group, took advantage of this and seized the southern port city of Aden, then controlled by government forces. STC had accused Mr Abed Rabbo of mismanagement and colluding with the Islamist forces. A peace deal brokered by Riyadh, which briefly allowed Mr Abed Rabbo to regain control, was later ignored. In April, the STC declared self-rule in southern Yemen. That same month, Saudi Arabia announced a unilateral ceasefire because of the coronavirus pandemic.

Yemen has suffered the world's worst humanitarian crisis in recent years. The UN estimated that four in five Yemenis need humanitarian aid. Yemen has also struggled with the biggest cholera outbreak on record since the war started. The UN warned that the death toll from the coronavirus pandemic could "exceed the combined toll of war, disease and hunger over the last five years". The nearly four million people who have been displaced could set off a wave of refugees across the region.

As the war drags on, Yemen became a battleground for proxy powers between Shi'ite Iran and Sunni Saudi Arabia. In the south, the government forces are accused of forging alliances with extremists and other militias. Terror groups like the Islamic State in Iraq and Syria and Al-Qaeda have been exploiting the political instability in Yemen to build strength.

The crisis could also disrupt the world's oil shipments, much of which pass through the Gulf of Aden, where Yemen is situated.

The crisis may have started in 2011 but the animosity between the country's north and south dates back to the civil wars of the 1960s.

Mr Abed Rabbo is unpopular in the north. The STC has very little support outside Aden. And the Houthis are generally received with hostility in the Sunni-majority south. Peace deals have been forged and broken. Some pondered the possibility of a southern secession. But without a single force that could hold the country together, peace in Yemen remains an elusive idea.