Prior to the official U.S. entry into the Second World War, American merchant ships carried needed supplies that supported the Allies in their desperate struggle against the Axis powers. Although German aircraft and submarines attacked American merchant ships when they entered war zones, the U.S. Neutrality Act of 1936 prevented them from being armed, even for self defense.
Pressure began to build for a change, and many sought to resurrect the idea of the Armed Guard Service, used during the First World War. Congress amended the Neutrality Act on 17 November 1941, barely three weeks before Pearl Harbor, to allow the U.S. Navy to arm merchant ships.
The section under the Navy Department for directing the Armed Guard Service during World War II, Op-23L, formulated doctrine, improved training, and overcame shortages of personnel and equipment. Primarily intended to protect the ship from enemy aircraft and submarines, the Navy’s standard Armed Guard detachment consisted of one 5-inch dual purpose gun, one 3-inch anti-aircraft gun and eight 20mm machine guns manned by one officer, 24 gunners and 3 communications personnel, the latter for liaison with Navy warships and shore stations.
The often overlooked service was a huge and expensive effort. Over the course of the war, the Navy armed 6,236 merchant ships and placed Armed Guards on almost all the 5,114 U.S. owned ships, a task requiring almost 145,000 personnel in service. Many of those ships were attacked at sea or in foreign harbors and the enemy sunk 569 U.S.-flagged ships at a cost of 1,810 men. Over 8000 of those that served in the Armed Guards received decorations or commendations, including five Navy Crosses, two Legions of Merit, and seventy-five Silver Stars.
The training and armament of these detachments gave U.S. merchant ships the chance to fight off enemy air attacks and the firepower to engage enemy submarines.