Ten years ago Yemenis rose up against corruption and economic hardship, and demanded a more accountable and inclusive government. The country fractured politically and is now stuck in a war that has created what the United Nations describes as the world's biggest humanitarian crisis.
The following is a timeline of Yemen's slide into conflict.
1990: Unification of north and south Yemen to form a single state under President Ali Abdullah Saleh.
1994: Civil war in which Saleh prevents south, angered by what it sees as its lower status, from splitting with north.
2003-09: Houthi group in north protests marginalisation of the local Zaydi Shi'ite Muslim sect and fights six wars with Saleh's forces and one with Saudi Arabia.
2011: Arab Spring protests undermine Saleh's rule, lead to splits in the army and allow al Qaeda in the Arabian Peninsula (AQAP) to seize territory in the east.
2012: Saleh steps down in a political transition plan backed by Gulf states. Abd-Rabbu Mansour Hadi becomes interim president and oversees a national dialogue to draft a more inclusive, federal constitution.
2013: AQAP survives military onslaught and drone strikes, staging attacks across the country while retaining a persistent presence. Saleh and his allies undermine the political transition.
2014: The Houthis rapidly advance south from Saadeh and seize Sanaa on Sept. 21 with help from Saleh. They demand a share in power.
2015: Hadi tries to announce a new federal constitution opposed by the Iran-aligned Houthis and Saleh, who arrest him. He escapes, pursued by the Houthis, triggering Saudi intervention in March along with a hastily assembled Arab military coalition.
Months later the coalition, aiming to restore Hadi's ousted government, drives the Houthis and Saleh loyalists from Aden in south Yemen and Marib, northeast of Sanaa, but the frontlines solidify, setting up years of stalemate.
2016: AQAP takes advantage of the chaos to establish a mini-state around Mukalla in east Yemen, raising fears the war will lead to a new surge in jihadist activity. The UAE backs local forces in a battle that ends the group's rule there.
Hunger grows as the coalition imposes a partial blockade on Yemen, accusing Iran of smuggling missiles to the Houthis alongside food imports, something it denies.
Coalition air strikes that kill civilians prompt warnings from rights groups but Western support for the military campaign continues.
2017: The Houthis fire a growing number of missiles deep into Saudi Arabia, including at Riyadh. Seeing a chance to regain power for his family by reneging on his Houthi allies, Saleh switches sides, but is killed trying to escape them.
2018: Coalition-backed forces, including some flying the southern separatist flag, advance up the Red Sea coast against the Houthis, aiming to take the port of Hodeidah. Hodeidah handles the bulk of Yemen's commercial and aid imports and is critical for feeding the population of 30 million.
Military stalemate ensues. The Houthis control the port and coalition-backed Yemeni forces mass on the outskirts.
In the first major breakthrough in peace efforts, the warring parties agree at December talks in Sweden, the first in two years, on a ceasefire and troop withdrawal from Hodeidah. Work on a prisoner swap begins.
2019: The Stockholm Hodeidah truce largely holds but the withdrawal fails to materialise amid deep mistrust. Violence continues in parts of Yemen outside Hodeidah.
The UAE largely withdraws from Yemen while still supporting local allies, including southern separatists who in August seize Aden. Riyadh brokers a power-sharing deal between separatists and Hadi's government but implementation only begins in 2020.
2020: The coronavirus pandemic triggers a temporary UN-backed truce but no progress is made in talks to forge a permanent ceasefire and violence continues though the warring sides carry out a prisoner swap. The United Nations warns Yemen is on the brink of famine once more.
An attack on Aden airport moments after a plane lands carrying the newly formed power-sharing government kills at least 22 people. Riyadh and Hadi's government blame the Houthis.
2021: The Trump administration designates the Houthis as a foreign terrorist group, prompting warnings from the UN that the move could tip Yemen into a large-scale famine and chill peace efforts. New US President Joe Biden's administration says it will allow all transactions for a month while it reviews the designation.