As a part of the Emergency Shipbuilding Program, the U.S. Maritime Commission, in addition to the construction of cargo ships and tankers, also built many commissioned U.S. Navy vessels. Between 1939 and 1945, the commission oversaw the delivery of 682 “military” type vessels.

The navy used Maritime Commission-built Attack Cargo Ships and Attack Transports to deliver troops and material during amphibious assaults, and to provide additional fire support during landings. Many of these ships were essentially fast-and well-protected versions of standard Commission designs; in fact, some military hulls originally began construction as standard cargo ships in the Long Range Shipbuilding Program before the Maritime Commission transferred them to the navy’s control.

The Maritime Commission also constructed many combatant vessels, including escort aircraft carriers, Landing Ship Tanks (LSTs), and patrol frigates.

The Maritime Commission contracted for these vessels, rather than the U.S. Navy, for two reasons: only Maritime Commission-contracted yards had the capacity to handle the construction and many of the hulls, especially those of the auxiliary vessels, used Maritime Commission designs.

After the war, the navy transferred many of these vessels back to the Maritime Commission. While the Commission laid up many of these ships in the National Defense Reserve Fleet to serve in future crises, it also sold many to commercial shipping companies. After the removal of military features, these merchant hulls served as a large part of the postwar U.S.-flag fleet.