President Donald Trump on Saturday ordered airstrikes in Yemen’s capital, Sanaa, against Iranian-backed Houthi rebels, who have attacked merchant ships and U.S. forces in the region.

“[The Houthi] have waged an unrelenting campaign of piracy, violence, and terrorism against American, and other, ships, aircraft, and drones,” Trump wrote on Truth Social. “No terrorist force will stop American commercial and naval vessels from freely sailing the Waterways of the World.”