Some of the largest shipping companies in the world have been forced to reroute their vessels at considerable costs after Yemen’s Houthi group targeted ships headed towards Israeli ports in solidarity with Palestinians.

The Iran-aligned group has demanded that Israel allow humanitarian aid to enter Gaza, which has been reeling from more than two months of Israeli siege and bombardment. The Yemeni group has also called on Israel to end its brutal war on Gaza that has killed over 19,000 Palestinians.

The United States on Tuesday announced the formation of a 10-nation coalition to deter the attacks that threaten to disrupt trade passing through one of the busiest maritime routes in the world.

Let’s take a look at who the Houthis are, just how much they are disrupting global trade, and what they can hope to achieve from it.

Who are the Houthis?

The Houthis rebelled against Yemen’s internationally recognised government in 2014, starting fighting that led to a civil war that caused a devastating humanitarian crisis in the impoverished Arab nation.

For years, with backing from Iran, they fought a military coalition led by neighbouring Saudi Arabia that also included Western and regional allies. However, the Yemeni conflict became a stalemate, with Saudi Arabia deciding to begin peace talks with the group after years of war.

Also known as Ansar Allah, they now remain in control of most parts of Yemen, including the capital Sanaa and some of the western and northern parts close to Saudi Arabia.

They command a considerable military arsenal, which includes a variety of drones and missiles – including ballistic antiship missiles that they have for the first time ever successfully used against vessels in the Red Sea.

Earlier this year, Saudi Arabia agreed with Tehran, a close Houthi ally, to restore formal diplomatic ties after a seven-year rift.

Who are they attacking?

The Houthis first launched missiles and drones at southern Israel in October, but they either did not reach their far-away targets – some 2,000km (1,240 miles) away – or were intercepted by Israel and its allies.

But as Tel Aviv kept refusing international calls for a ceasefire, they significantly ramped up their strikes, leveraging their position near the Red Sea, and especially close to the narrow Bab al-Mandeb Strait that connects the Gulf of Aden to the southern part of the sea.

They have seized and kept in their ports a commercial vessel, they have attacked several more trade ships carrying everything from vehicles to foodstuffs, and the Pentagon claims some of their projectiles were travelling in the direction of US warships before being shot down.

The Houthis have said ships with no links with Israel will have nothing to worry about, and they will only target vessels owned by Israel or taking goods to and from Israel. But tracking ownership of ships can be difficult, and some targeted companies have denied having ties with Israel.