During the war, losses of merchant shipping to submarine warfare on the North Atlantic had become so severe that shipbuilding production had become a major strategic issue. In the United Kingdom, at that time the world’s leading shipbuilder, capacity was expanded and between 1917 and 1921 the United States set up the first mass-production facility for merchant ships at Hog Island. The facility, which had 50 slipways, was designed to build 7800 dwt freighters for the war effort. However, it did