SANA, Yemen — A drone aircraft attacked a group of people preparing to attack Yemeni troops on Thursday, killing at least nine, including a man identified as a leader of the local branch of Al Qaeda, according to Yemeni and security officials, who said the drone was American-operated. The strike took place less than a mile from a Yemeni brigade’s position in the southern province of Abyan, the officials said, adding that troops from the brigade found and defused an explosive belt that was wrapped around the waist of one of the dead, identified as Nader Al Shaddadi, one of...