The U.S. military is not joining the Saudi-led Arab coalition’s war against Houthi rebels in Yemen, the Pentagon said Thursday.

A Pentagon spokesman said the U.S. Tomahawk cruise missile attack launched early Thursday morning from the destroyer USS Nitze against three coastal defense missile radar sites in Yemen was a purely defensive response to attacks on a U.S. ship, and does not signal wider U.S. involvement in Yemen’s civil war.