The aft gun platform contained the ship’s primary defensive armament. The guns on this platform could range from a 3-inch 50 caliber to a 5-inch 38 caliber, along with two of the ship’s eight 20mm Oerlikon antiaircraft cannons.
During the war, the O’Brien had a 3-inch gun mounted here that was identical to the one mounted at the bow. Today, the gun you see here is a 5-inch 38 caliber, which was the largest mounted on Liberty ships. It was capable of engaging enemy ships or aircraft by firing a 55-pound projectile up to a distance of ten miles.
All the guns on the O’Brien were removed in 1946 by the US Navy before the ship was placed into the reserve fleet at Suisun Bay. Like the forward 3” gun, it was also sourced from the US Navy commissioned Liberty Ship, USS Palawan.
Each gun had a ready supply of ammunition stored in lockers nearby and in magazines below the gun decks. When the Naval Armed Guard did not have enough personnel to adequately man the guns, trained Merchant Marine crew were assigned to battle stations to complement the gun crews.
Another visible feature on the aft gun platform is an emergency steering wheel, which could be used if the steering gear on the bridge failed.
Explore this Station's Gallery
Descend the gun platform to explore the essential equipment at the stern.