Two U.S. Navy sailors stand watch at a .50 caliber Browning machine gun mounted in an open gun tub aboard ship, scanning the horizon for enemy aircraft. One crewman wears a sound-powered telephone headset beneath his helmet, maintaining communication with the ship's gunnery control station. Anti-aircraft gun crews like this one stood ready around the clock during World War II, providing the last line of defense against air attack for vessels operating in contested waters. Project: 218048