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. Although the basic design itself was obsolete even before the first one slid down the builder's ways, it had the advantage of being relatively easy to produce, and simple to operate and maintain. Thus, the vessels were mass-produced by no fewer than eighteen shipyards. Building time, initially 244 days, dropped to forty-two days per ship, although as a publicity stunt the Robert E. Peary was launched four days and fifteen and a half hours after the keel was laid.