Liberty Ships: America's Merchant Marine Transport in World War II. David Doyle. 9" x 9". Although not a weapon in the traditional sense of the word, arguably no item in the Allied arsenal contributed as much to the defeat of the Axis during WWII as did the Liberty ships. The 2,710 Liberty ships placed into service between 1941 and 1945 provided a vital link in the supply chain not only of US but also Allied forces during WWII.