5. Liberty ships carried armament with which to defend themselves
Liberty ships were conceived and built to operate within the convoy system across the Atlantic from Canada and the United States. In the convoy system, protection for the merchant ships came primarily from the escort vessels. Experience prior to 1941 indicated convoys often needed to disperse as a result of German submarine and surface raider attacks. The designers thus gave Liberty ships some means of self-defense, in the form of a 3-inch gun forward, a 4-inch gun aft, and anti-aircraft machine guns and cannons. Later versions replaced the aft 4-inch gun with a more powerful 5-inch. The guns offered a means of defending the ship against surfaced submarine attacks, and the ship could protect itself from airborne attacks. Against a submerged submarine it remained virtually helpless, entirely dependent on the naval escorts.
Because merchant seamen were not trained gunners, Navy contingents sailed in the Liberty ships. Usually between 12 and 25 naval gunners sailed as supernumeraries, reporting to their own commanding officer rather than the ship’s master. The US Navy sailors were usually considerably younger than their civilian counterparts, with far less time at sea. On some ships, members of the civilian crew received training from the Navy in the operation of the guns. The training provided emergency backups should casualties reduce the efficiency of the Naval contingent (called the Armed Guard). In the Pacific ships often traveled independently, without naval escort, especially in the waters between the West Coast and the Hawaiian Islands, and along the coasts of Australia and New Zealand. They too carried Naval gunners to provide defense against Japanese attacks. Despite the defenses, over 200 Liberty ships were lost over the course of the war.