During the Battle of Tarawa, Major Ryan landed on Betio Island under heavy enemy fire on November 20, 1943. After his company was almost wiped out, he had rallied the survivors of his unit, two M4 Sherman tanks and other Marines from infantry and machine gun platoons scattered on the beach, from which he formed a composite battalion and attacked. Ryan, who had been thought to be killed in action, arranged for naval gunfire and mounted an attack that cleared the island's western end. Thanks to his actions, the first substantial reinforcements landed intact after two days of heavy fighting.