Who are the Houthis and why did the US and UK retaliate for their attacks on ships in the Red Sea?

WASHINGTON — When U.S. and U.K. warships and aircraft launched waves of missiles at Iranian-backed Houthi rebels in Yemen early Friday in Sanaa, it capped weeks of warnings to the militant group to cease their drone and missile attacks against commercial vessels in the Red Sea or face severe consequences.

Previously the U.S. had withheld striking back, reflecting larger U.S. concerns about upending the shaky truce in Yemen and triggering a wider conflict in the region. But on Tuesday the Houthis launched their largest-ever barrage of 18 one-way attack drones, anti-ship cruise missiles and an anti-ship ballistic missile at a host of international commercial vessels and warships in the Red Sea.

While the U.S. and partner military ships and aircraft now protecting the waterways were able to deflect Tuesday’s attack, the scope and severity of the launch drew international condemnation and left few options other than to carry through with international warnings that any further attacks would draw a substantial response.

In response, the U.S. and U.K. struck Houthi missile, radar and drone capabilities to degrade the group’s ability to conduct more attacks like Tuesday’s barrage.

In response to the strikes, which occurred in Yemen just before Friday 3 a.m. local time, the militant group has already pledged to retaliate.

Here’s a look at the Houthis and their increasing attacks, and why the U.S. believes it is more acceptable to bomb some Iranian-linked targets than others.

WHO ARE THE HOUTHIS?

Houthi rebels swept down from their northern stronghold in Yemen and seized the capital, Sanaa, in 2014, launching a grinding war. A Saudi-led coalition intervened in 2015 to try to restore Yemen’s exiled, internationally recognized government to power.

Years of bloody, inconclusive fighting against the Saudi-led coalition settled into a stalemated proxy war between Saudi Arabia and Iran, causing widespread hunger and misery in Yemen, the Arab world’s poorest country. The war has killed more than 150,000 people, including fighters and civilians, and created one of the world’s worst humanitarian disasters, killing tens of thousands more.

A cease-fire that technically ended more than a year ago is still largely being honored. Saudi Arabia and the rebels have done some prisoner swaps, and a Houthi delegation was invited to high-level peace talks in Riyadh in September as part of a wider détente the kingdom has reached with Iran. While they reported “positive results,” there is still no permanent peace.

ATTACKS ON SHIPS

The Houthis have sporadically targeted ships in the region over time, but the attacks have increased since the start of the war between Israel and Hamas and spiked after an explosion Oct. 17 at a hospital in Gaza killed and injured many. That hospital blast marked the beginning of an intense militant campaign against U.S. bases in Iraq and Syria, and on many commercial vessels transiting the Red Sea. The attacks have damaged commercial ships and forced international shipping companies to divert their vessels around the Cape of Good Hope.

As of Thursday the Houthis had launched 27 different attacks on vessels transiting the Southern Red Sea, Pentagon spokesman Maj. Gen. Pat Ryder said at a Pentagon press conference.