Yemen’s Houthi rebels seized control of the country's capital in late 2014, starting a civil war that still rages and has led to the government calling for a Saudi-led coalition to intervene and restore the internationally recognised administration.
The rebels have taken over vast areas of the north and centre of the country, purging pro-government figures from the civil service and public life, establishing their own school curriculum and indoctrinating thousands of youth at summer camps.
Saudi and Emirati air defences shoot down many projectiles, but civilians have been killed and injured and civilian infrastructure has suffered damage.
So, who are the Houthis and what do they want to achieve?
Who are Yemen’s Houthi rebels?
Also known as Ansar Allah, the Proponents of Allah in English, the Houthis are an armed Islamist militia and tribe from north Yemen's poor, mountainous Saada region.
While the Houthis originate from the minority Zaydi offshoot of Shiite Islam, they have evolved from a religious group into a militia and political force.
Yemen’s former President Ali Abdullah Saleh was also Zaydi and ruled Yemen for 33 years.
In the 1990s, a separatist Islamist, Hussein Badreddin Al Houthi, who was believed to have close ties to Iran, led an uprising against him.
As security in the region began to deteriorate during the US invasion of Iraq, the Houthis adopted their infamous slogan: “God is great, death to the US, death to Israel” which is often still seen on signs and heard at rallies.
Lebanon’s Hezbollah, and its leader Hassan Nasrallah, became role-models for the Houthi rebels and their leader Abdulmalik Al Houthi.
Experts point to rhetorical and stylistic similarities in the speeches of the two leaders and reports indicate some Houthi media officials are based in Beirut.
How did they take Sanaa?
In 2011, mass protests against Saleh were met with deadly police violence. Amid escalating international condemnation, the president left the country and agreed to the Gulf Co-operation Council's transition plan and Abdrabu Mansur Hadi became president.
The Houthis launched an offensive south from Sadaa to the capital and swept into the city in 2014 demanding President Hadi form a unity government that they were part of.
They then refused to participate in this new administration, even shelling the president's palace on several occasions, before seizing power and ousting Mr Hadi and his cabinet in 2015.
The Houthis constitutional declaration was rejected by the international community and many Yemenis. Mr Hadi and several ministers managed to flee Sanaa for Aden and called in the Gulf coalition.
What do they want?
With large areas of the country’s north under their control, the Houthis continue their battle against the Saudi-led coalition to take over the entire country.
Yemen is now suffering the world’s worst humanitarian crisis and the Houthi rule of Sanaa and their harassment of journalists has resulted in a media blackout on reporting the deteriorating conditions in the country’s medical infrastructure, economy and quality of life.
Who are the Houthi leaders?
Abdulmalik Al Houthi, brother of the Houthi movement's founder Hossein Al Houthi, was a key player in building the movement from a small group of Zaydi sect members to a force that has taken over large parts of Yemen.
Under his command, the Houthis took Sanaa in 2015, killed Saleh in 2017, and capitalised on Iranian and Iran-backed Hezbollah military know-how.
The US Treasury Department said sanctioned Houthi military leader Abdullah Yahya Al Hakim was “implicated” in the 2015 coup against President Hadi.
The US says Al Hakim “met with military and security commanders, tribal chieftains and leading partisan figures loyal to former President Saleh,” whose son Ahmed Saleh, is a Houthi loyalist, and was sanctioned by the US.
The military commander of the Houthi movement, Abd Al Khaliq Badr Al Din Al Houthi was born in 1984 and is known as Abu Younes. He is one of eight brothers including Houthi founder Hossein and current leader Abdulmalik Al Houthi.
He was blacklisted and placed under sanction by the UN on November 7, 2014, and by the US the following year.
The Yemeni government says he played a pivotal role in the takeover of Sanaa.
The US believes he led Houthi fighters in deadly attacks on several locations during the siege of Dammaj in 2013, blowing up a school for teaching the Quran.
He also had a role in moving weapons and allegedly ordering an attack against diplomatic institutions, according to the US State Department.