The Houthis, also known as Ansar Allah (or “supporters of God”), are a violent militia group that currently exercise de facto control over much of northern Yemen. Formed in the 1990s, the group was named after its founder, Hussein Badreddin al-Houthi, and they follow the Zaidi branch of Shia Islam which represents 20-30% of Yemen’s population.

The group’s leadership has been drawn from the Houthi tribe, which is part of one of the three major tribal confederations in Yemen: the Hashid, the Madhaj and the Bakil. The Houthis are part of the Bakil confederation, the largest tribal group in Yemen. As the UK and US launch military strikes on the Yemeni group, after a spate of attacks by the Iran-backed militia on Red Sea shipping, here’s four things that you need to know about them.

1. Why did the Houthis form?

In order to understand the rise of the Houthis, it’s first important to lay out the turbulent history of Yemen. Yemen has struggled to build a unified and effective state and has been plagued by weak institutions, weak nationalism, insurgency and secessionism since its formation in 1990. The area that comprises Yemen today was split into two territories, north and south from the 19th century to 1990. After the collapse of the Ottoman empire, North Yemen became independent in 1918. The south of Yemen was under British control until 1967. The People’s Democratic Republic of Yemen (South Yemen) was independent from 1967 to 1990. The two were unified in 1990.

Tribal identities remain strong, particularly in the north, and many different groups have held power. The Zaydi Shiites have fought for control of the territory that we now know as Yemen for thousands of years, with some success, and under the Houthis, control parts of northern Yemen.

If we fast forward to the modern era, Yemen has faced constant conflict and state failure. The north was ruled by former Yemeni president Ali Abdullah Saleh (a dictator who is part of another tribal group), since 1978, who then took over as president of a newly unified Yemen in 1990 . Saleh’s relatives controlled core parts of the army and economy – and corruption was rife.

Tensions arose over the vast majority of Yemen’s resources flowing to Sana'a, the capital of north Yemen, and in particular to Saleh’s Sanhan clan, which is a part of the Hashid federation. Though the central government managed to keep the country together (Saleh notably claimed that ruling Yemen was like “dancing over the heads of snakes”) after the south attempted to secede in 1994, there were many groups that held grievances against the Saleh-led government.

The most notable group to challenge the central government in Yemen were the Houthis. In addition to enduring decades of political marginalisation, neglect, economic exclusion and sometimes terror by the central government, the Houthis were concerned by rising Saudi influence in the country — and with the growing power of Salafism and Wahhabism (seen as imported Saudi religious doctrines) in particular.

But the tipping point for the Houthi movement was likely the US invasion of Iraq in 2003. Influenced by the success of Lebanon-based militants Hezbollah in repelling western forces, the Houthis drew inspiration and gained support from the Lebanese-based group, as well as Iran — though their officials deny their connection.

2. How did the Houthis gain power?

To address the growing power of the Houthis, Saleh launched a military campaign in 2003, with the help of Saudi Arabia. Though Saleh’s forces managed to kill Houthi leader, Hussein al-Houthi in 2004, the Houthis often bested Saleh and the Saudi army in spite of billions of dollars spent by the latter.

Indeed, the Houthis proved to be a formidable force for the Saudis to contest with, daring to cross into Saudi Arabia in 2009, and forcing the kingdom to deploy its army to address the growing Houthi threat.

Since the Yemeni revolution erupted in 2011, the Houthis fought to oust Saleh from power, only to later join forces with Saleh in 2015. When their alliance crumbled, it was the Houthis who had the upper hand, with the rebel group killing Saleh in December 2017.

The Houthis have also been a major force in the ongoing Yemeni civil war (which began in 2014), which has caused an estimated 377,000 deaths, many of them civilians. Though it is the government in the south that is internationally recognised, the Houthis have taken over much of northern Yemen, since they stormed Sana'a in 2014. They control the key port of Hudeidah, which generates up to US$1 billion (£784,000,000) in revenues for the Houthi government.

A map of Yemen. Matthew Nichols1/Shutterstock

3. What is their regional influence?

Today, the Houthis have an estimated 20,000 fighters. Since the death of al-Houthi, the movement has been primarily led by his brother, Abdul-Malik al-Houthi, who has stated that he will not hesitate to attack the US and its allies.

Since the war started in Gaza in October, the Houthis have tried to capitalise on the conflict to raise their international profile, and as a show of power that could gain them more negotiating influence. Claiming to be in solidarity with the Palestinian people, the Houthis initiated a series of attacks on commercial ships in the Red Sea, the narrow northern end of which is overlooked by Yemen. The most brazen attack took place on November 19 2023, when militants used a helicopter to abduct the crew of a car carrier that was linked to an Israeli businessman.

4. Do they control Red Sea access?

Though most of the Houthi attacks on the Red Sea have not been successful, they have forced thousands of ships to bypass the route and divert around South Africa—adding significant costs and time.

In retaliation for the dozens of attacks on the Red Sea, the US and the UK have responded with their largest attack against the Houthis since 2016 , when the US struck three Houthi missile sites with cruise missiles after the Houthis fired on the US navy and commercial vessels. This called a temporary halt to Houthi attacks. But now, with the Houthis confident that they have been victorious against the Saudis and the west in Yemen, the rebels seem more eager than ever to take on the US head on.