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

WASHINGTON (AP) — 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 ships and warships in the Red Sea.

While the U.S. and partner military ships and aircraft protecting the waterways were able to deflect the 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 to the attacks Friday, which struck in Yemen just before 3 a.m. local time, the militant group has already pledged to retaliate.