Impoverished Yemen has been mired in devastating conflict between Iran-backed rebels and troops loyal to President Abedrabbo Mansour Hadi since 2014.
The war escalated in 2015 when a Saudi-led military coalition intervened on the side of government after the Huthi rebels seized the capital and several provinces.
Here is an overview:
In July 2014 Huthi fighters, who have opposed the central government for a decade, launch an offensive from their northern stronghold of Saada.
In September they enter the capital Sanaa, seizing the government's headquarters.
The rebels ally themselves with military units loyal to ex-president Ali Abdullah Saleh, who was forced to quit after a 2011 uprising.
In October they capture the vital Red Sea port of Hodeida.
In January 2015, after fierce battles in Sanaa, the Huthis seize the presidential palace and surround the residence of the new president, Hadi, who flees south to the city of Aden.
A Saudi-led coalition enters the conflict in March 2015 with air strikes on rebels.
The Shiite Huthis are backed by Iran, a bitter rival of Sunni power Saudi Arabia.
As the rebels advance on Aden, Hadi quits the city amid intense fighting and takes refuge in the Saudi capital, Riyadh.
DE FACTO CAPITAL
In July his embattled administration announces its forces have retaken the entire province of Aden, their first success since the coalition stepped in.
The city of Aden becomes the country's de facto capital, with Sanaa still in rebel control.
By August pro-government forces have retaken five southern provinces.
In October government forces reclaim control of the Bab al-Mandab Strait, an internationally vital shipping route off Yemen's coast.
In August 2016 lengthy UN-brokered negotiations in Kuwait between the government and rebels collapse after failing to reach a power-sharing deal.
Splits emerge in the rebel camp in 2017 after Saleh makes overtures to the Saudi-led coalition.
Armed clashes rock Sanaa and in December the former president is assassinated by his former Huthi allies.
In June 2018 government fighters, backed by Saudi and Emirati forces, launch an offensive to retake the rebel-held port of Hodeida, a vital entry point for food imports and international aid.
Within days they say that they have taken control of the city's airport, but they halt their advance to allow negotiations.
The UN-brokered peace talks in Geneva in September fail, with the rebel delegation refusing to attend, and the offensive resumes.
In November 12 days of bombardment and fighting leave some 600 people dead, mostly fighters from both camps.
On October 30 the United States makes a surprise call for a ceasefire and a halt to air strikes. Britain joins the push for peace.
UN envoy Martin Griffiths flies into Sanaa on November 21 for talks with rebel leaders. Days later he meets Yemeni officials in Riyadh.
Griffiths returns to Yemen on December 3, shortly before 50 wounded rebels are flown out on a UN charter flight for medical treatment in neighbouring Oman.
The next day a rebel delegation leaves with Griffiths heading for peace talks in Sweden, hours after the government and rebels agree to swap hundreds of prisoners.
According to the World Health Organization, around 10,000 people have been killed in the conflict, though some rights groups estimate the toll could be five times higher.
The toll has been particularly heavy on civilians, who have been caught up in air strikes often blamed on the Saudi-led coalition.
UN agencies say up to 14 million Yemenis are at risk of starvation.
Save the Children says that between March 2015 and October 2018 some 85,000 children under five may have died of severe malnutrition or related diseases.
The UN children's fund has described the conflict as "a living hell for every single boy and girl in Yemen".