After a trip back to Georgia, Lamar returned to Texas. Learning of a battle for independence, he traveled with his horse and sword to join Sam Houston's army in spring 1836, and distinguished himself with bravery at the Battle of San Jacinto. On the eve of the battle, Lamar courageously rescued two surrounded Texans, an act that drew a salute from the Mexican lines. One of those rescued was Thomas Jefferson Rusk, later appointed as Texas Secretary of War. Lamar was promoted that night from private to colonel and given command of the cavalry during the battle the following day.