Complex sentence: Mansel was captured during the Antiochene cavalry attack, and Baibars ordered him to command his lieutenants in Antioch to surrender immediately to him, but the garrison refused to capitulate, and continued the defense of the walls.
Split into simpler sentences: Mansel was captured during the Antiochene cavalry attack, and Baibars ordered him to command his lieutenants in Antioch to surrender immediately to him. The garrison refused to capitulate, and continued the defense of the walls.