The conflict in Yemen intensified on Sunday, as government forces launched attacks against Iran-backed Houthi rebels along the Red Sea and Houthis fired into neighboring Saudi Arabia, which supports Yemen’s government. The Yemeni government vowed to send more forces to the Red Sea coast and one official conceded a “painful” defeat last week when Houthis captured the port city of Mokha and an island on the Bab el-Mandeb Strait, a crucial shipping alternative to the Strait of Hormuz.