Impoverished Yemen is mired in a devastating conflict between Iran-backed rebels and government forces that intensified after Saudi Arabia spearheaded a military intervention five years ago.
Here is an overview, after a deadly explosion at Aden airport killed more than two dozen people in what officials say was an attack by rebels.
– Saudi-led intervention –
In September 2014, Huthi rebels from the country’s Zaidi Shiite minority in northern Yemen enter the capital Sanaa, seizing the government headquarters.
Backed by Shiite-majority Iran, the rebels ally themselves with military units loyal to ex-president Ali Abdullah Saleh, who was forced to quit after a 2011 uprising.
As well as the capital, they seize swathes of territory, including the Red Sea port of Hodeida, a crucial entry point for imports and humanitarian aid.
In February 2015, President Abedrabbo Mansour Hadi flees to second city Aden.
A coalition led by Sunni-ruled Saudi Arabia, the bitter regional rival of Iran, enters the conflict on March 26, 2015 with air strikes on the rebels.
Washington says it is contributing logistics and intelligence.
As the rebels advance on Aden, Hadi flees, taking refuge in Saudi Arabia.
The coalition’s intervention helps pro-government forces to secure the southern port city and in October they announce they have retaken control of the Bab al-Mandab Strait, a key waterway for international shipping.
– Battle for aid port –
In June 2018, government fighters, backed by Saudi and Emirati ground forces, launch an offensive to retake the port city of Hodeida.
UN-brokered talks between the warring parties open in December, yielding a series of breakthroughs including a ceasefire in Hodeida where fighting largely stops.
– Southern separatists –
The anti-Huthi camp is divided, with fighting breaking out repeatedly between southern separatists and unionist forces loyal to Hadi’s government.
In January 2018, the separatists occupy the presidential palace in Aden, before Saudi and Emirati forces intervene.
South Yemen was an independent state until unifying with the north in 1990, and separatists remain powerful.
In August 2019, separatists in Aden from the UAE-trained Security Belt force clash with unionist troops backed by Riyadh.
In November, a power-sharing accord is signed between the two parties, but is never implemented.
On April 26, 2020, the separatists declare self-governance for the south, and the accord with the government crumbles.
– New escalation –
On January 18, a missile strike on a loyalist military camp in the northern town of Marib blamed on the Huthis kills 116 people and injures dozens.
In March, the rebels seize Al-Hazm, provincial capital of Al-Jawf province north of Sanaa, after heavy fighting with government troops.
In August, the army launches a counter-offensive in Al-Jawf province.
– Prisoner swap –
In a rare sign of progress, the biggest prisoner swap between rebels and the government since the start of the conflict takes place in October, with more than 1,000 fighters freed over two days.
The swap comes after the release of two Americans held captive in Yemen, in an apparent swap for some 240 Huthi supporters allowed to return home.
But in a fresh escalation in November, rebels launch a missile attack on a Saudi Aramco oil facility in the Red Sea city of Jeddah.
– Unity government –
On December 18 the government and southern separatists form a new cabinet, forging a joint front against the rebels.
But on December 30, moments after the new unity government lands in Aden, explosions rock the airport, killing at least 26 people. Officials call it a “cowardly” attack by the rebels.
Since it began, Yemen’s conflict has killed tens of thousands of people, mostly civilians, relief agencies say.