The US has carried out a round of attacks against the Houthis in Yemen, targeting five underground weapons depots with B-2 stealth bombers.

Here's what you need to know about the attack:

Who are the Houthis and why is the US attacking them? The Houthis are part of an Iran-backed alliance of militant groups in the Middle East.

The alliance, which includes Yemen, Syria, Gaza and Iraq, has been attacking Israel since the start of the Israel-Hamas war. The Houthis say they will not stop attacking Israel and its allies until a ceasefire is reached in the Palestinian enclave.

Although they do not pose as big a threat to Israel and the United States as other Iranian proxies such as Hamas and Hezbollah, the Houthis have for months targeted ships in the Red Sea, one of the world's busiest waterways in the Gaza Strip, in response to the war.

Austin said he authorized the U.S. strikes at the direction of President Joe Biden to “further weaken” the Houthis' capabilities after more than a year of the Houthis attacking U.S. and international ships in the region. The facilities contained “various weapon components” that would be used to combat ships in the Middle East, the defense secretary said.

Why did the US use B-2 bombers? Thursday's attack marked the first time since the start of the Gaza war that the United States used the B-2 stealth bomber to attack the Houthis in Yemen. The B-2 is a much larger platform than the fighter jets previously used to attack Houthi facilities and weapons, and can carry a far larger load of bombs.

Austin said U.S. forces used the B-2 bomber to show the U.S. can target facilities “that our adversaries want to keep out of reach, no matter how deeply buried, fortified or fortified.” “

How did the Houthis react? A Houthi spokesman said: “America will pay the price for its aggression against Yemen, and as we have said before, its aggression will not deter Yemen from its stance in support of Gaza.”