Frank Caldwell joined the Marine Corps in 1942, and was assigned to the 1st Marine Parachute Battalion. He saw action on Guadalcanal, Vella La Vella, and Bougainville before the parachute battalions were deactivated and he was assigned to the 5th Marine Division. As commander of F Co., 2nd Bn, 26th Marines, he landed on Iwo Jima February 19, 1945. There, his men captured more ground than any other Marine company in the battle. Yet at the end of the battle, none of his officers remained, while F Co. suffered the highest KIA rate of any Marine company in U.S. history. Caldwell was awarded the Navy Cross for his valor on Iwo Jima.