Needing thousands of merchant ships to transport troops and supplies to Great Britain, the Allied nations were hard pressed to build enough tonnage to offset U-boat sinkings in the North Atlantic. Consequently, the U.S. Maritime Commission worked closely with the shipping industry to streamline traditional construction techniques. Using concepts based in part on those of Henry J. Kaiser, the time to build a typical merchant ship was cut drastically. They were crucial for the planning for D-Day.
A new generation of ships was conceived, designed, and built in American shipyards. Most numerous were the Liberty ship, officially the EC2 design. Composed of 250,000 prefabricated parts delivered in 250-ton sections, the Libertys were welded together in an average time of seventy days. The record was SS Robert E. Peary, completed in merely four and a half days. The first vessel, SS Patrick Henry, was launched 27 September 1941, and 2,750 sisters followed her off the ways. The average price for a Liberty ship was less than two million dollars.
When finished, a Liberty ship measured some 440 feet in length and was capable of accepting ten thousand tons of cargo in five holds. That amount equaled perhaps 2,000 jeeps, 440 light tanks, or 230 million rounds of rifle and machine-gun ammunition.
Propulsion was supplied by a steam engine fed by two oil-fired burners, developing 2,500 horsepower. Top speed was eleven knots, though most convoys were slower in order to accommodate all ships assigned.
A typical crew was composed of forty-four merchant seamen plus twelve to fifteen members of an Armed Guard gun crew.
Libertys were typically named for people, ranging from Abigail Adams to Wyatt Earp.
Liberty ships were augmented by Victory ships as well as tankers and military-owned transports. All were vital in sustaining the buildup to D-Day.
This article is part of our larger selection of posts about the Normandy Invasion. To learn more, click here for our comprehensive guide to D-Day.