Seven years have passed since Houthi rebels seized the Yemeni capital Sanaa in September 2014, sparking a war that has plunged the already impoverished country into the world's worst humanitarian crisis.
Despite diplomatic efforts to stop the fighting between the Iran-allied rebels and Saudi-backed government, there is no end in sight to a conflict that has put millions on the brink of famine.
Here are some of the key questions and answers about the war in Yemen.
How did the war start?
The Yemen conflict, as we know it today, has its roots in the Arab Spring revolt that forced Yemen's long-serving authoritarian president, Ali Abdullah Saleh, to hand up power to his deputy, Abdrabbuh Mansour Hadi, in 2011.
President Hadi faced a number of challenges as he took over, including jihadist attacks, a separatist movement in the south, security personnel's continued loyalty to Saleh, as well as corruption, unemployment, and food insecurity.
The Houthi movement (officially known as Ansar Allah), which represents Yemen's Zaidi Shia Muslim minority and launched a series of rebellions against Ali Abdullah Saleh over the preceding decade, took advantage of the new president's weakness by seizing control of Saada province and surrounding territories.
Yemeni fighters loyal to the Iran-backed Houthi rebels raise their weapons during a rally to express solidarity with the Palestinians, in the capital Sanaa, on May 20, 2021 / AFP
Many ordinary Yemenis, notably Sunnis, were disillusioned with the chaotic transition of power and backed the Houthis, who gained control of the capital Sanaa in late 2014 and early 2015.
After that, the Houthis and a fraction of security forces loyal to Saleh attempted to take control of the entire country, forcing president Hadi to flee overseas in March 2015.
Saudi Arabia and eight other predominantly Sunni Arab powers launched an air war to destroy the Houthis, eliminate Iranian influence in Yemen, and restore Mr Hadi's administration, alarmed by the rise of a group they felt was backed militarily by regional Shia power Iran. The US, UK, and France provided logistical and intelligence support to the coalition.
7 years on: Who has the upper hand?
Analysts say the balance has tilted in favour of the Houthi rebels against the Saudi-led military coalition.
Riyadh has been leading the coalition on behalf of the Yemeni government since March 2015, and its air strikes had allowed loyalists to reclaim southern territories from the rebels.
But the Houthis now appear stronger than ever, inflicting painful strikes on government forces as well as on targets in Saudi Arabia with a never-ending supply of ballistic missiles and drones.
Where is the biggest battle?
Despite heavy losses in recent months, the Houthis are again renewing their attempt to seize the city of Marib, the government's last northern stronghold.
The rebels first stepped up their campaign for Marib in February, leaving hundreds of dead on both sides. Taking over the city in the oil-rich province would strengthen their bargaining position in UN peace talks.
Fighters from a Saudi-backed Sudanese-Yemeni military force battling Huthi rebels are pictured in Hajjah governorate on May 23, 2021 /AFP
According to Peter Salisbury, an analyst at the International Crisis Group, a lot has changed in the past seven years.
"The Houthis have gone from being a relatively contained rebel movement to de facto authorities who (control) the capital and territory where more than 20 million people live," he said.
What is the UN doing?
Swedish diplomat Hans Grundberg, the UN's new envoy for Yemen, assumed his duties this week after his predecessor, Martin Griffiths, admitted his efforts over three years in the post had been "in vain."
Elisabeth Kendall, researcher at the University of Oxford's Pembroke College, said Grundberg's "main challenge will be finding a formula for a ceasefire that the Huthis can accept so that a peace process can begin."
While the United Nations and the US are pushing to end the grinding conflict, the rebels have demanded the reopening of Sanaa airport before any ceasefire agreement.
The last talks took place in Sweden in 2018, when the opposing sides agreed to a mass prisoner swap and to spare the city of Hodeida, where the port serves as the country's lifeline.
But despite agreeing to a ceasefire in Hodeida, violent clashes have since broken out between the rebels and pro-government troops around the strategic city.
What is the Human cost of the war?
Yemen has become the world's worst humanitarian disaster as the conflict continues to take a devastating toll on civilians. According to the UN, indirect causes like food insecurity and lack of access to health facilities have contributed to 131,000 of Yemen's projected 233,000 deaths since 2015.
Nearly 25 million Yemenis are still in need of help, five million are facing starvation, and a cholera outbreak has killed over a million people. Human rights and international humanitarian law have been allegedly violated by all sides of the war.
Is there hope for peace?
Peace in Yemen remains depressingly elusive.
Both the UN's Griffiths and Tim Lenderking, the US special envoy for Yemen, have toured the region to push peace efforts, without managing to find a resolution.
"Without considerable effort at a local level, no internationally brokered peace agreement will stick," said Kendall.
According to Madhaji, there are no positive indications in the near future.
"The situation will deteriorate further this year and the next if either party feels it is stronger than the other," he said.
"And the stronger party is usually not one to lean towards peace."
