The U.S. military struck Houthi-controlled sites from sea Wednesday, the fourth time the U.S. has attacked Yemen recently, according to The Associated Press.

The attack follows the Biden administration naming the Iran-backed Houthi group a Specially Designated Global Terrorist (SDGT), which the administration announced in a Wednesday statement. U.S. strikes on Yemen come “amid heightened tensions in the Middle East and fears that the Israel-Hamas war in Gaza could further spill out into the region,” CNN reported.

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Why is the U.S. striking Yemen?

The Yemen Houthis began attacking Red Sea vessels after the Hamas-Israel war that followed the Oct. 7 Hamas attack on Israel. The attacks have affected major shipping routes and freight rates.

Last week, a United Nations Security Council resolution called for an “immediate” end to Houthis attacks in the Red Sea, per BBC. President Joe Biden ordered strikes on Yemen for the first time following the resolution.

The initial U.S. military response also followed the “brazen” Jan. 9 Houthi attack on Red Sea vessels that spurred Biden “to move forward” on a military response following weeks of trying to pursue other options.

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Houthis vow retaliation after U.S., U.K. strikes in Yemen
What’s happening in the Red Sea?
Who are Yemen’s Houthis?

The Houthis have vowed to continue Red Sea attacks until Israel ends its Gaza military campaign.

Houthis, Iran and the U.S. strikes

Houthis striking a U.S. vessel preceded the latest attack on Yemen by a few hours, according to CNN. A Houthi strike damaged a U.S. vessel Monday, too.

Continued U.S. attacks on Houthi sites send a message to Iran as well, per AP.

“The U.S. has also strongly warned Iran to cease providing weapons to the Houthis. On Thursday a U.S. raid on a dhow intercepted ballistic missile parts the U.S. said Iran was shipping to Yemen,” according to AP.

Pentagon Press Secretary Maj. Gen. Pat Ryder said Wednesday that strikes on Houthi sites in Yemen would continue, AP reported.