The new shipways was also used to build destroyer escorts (DEs)—smaller, slower, and less expensive versions of destroyers designed for escort duty and antisubmarine warfare. Escorted convoys had proven to be the only effective way to thwart U-boat “wolf packs” preying on allied shipping. In 1942, after the Navy ordered the first of more than a thousand DEs, Charlestown built a new dry dock in which it could turn out four at a time. The next year 50 DEs were laid down at the yard, half of which were destined for Britain in accordance with the Lend-Lease Act of 1941. Charlestown got the production of DEs down to an art: of the 62 it built, workers launched an impressive 46 in the first eleven months of 1943. If 1941 was the year of the destroyer at the yard and 1943 belonged to the DE, 1944 was the year of the LST (Landing Ship, Tank). These seagoing assault vessels carried tanks and other vehicles during amphibious landings. The yard laid down 30 in 1944, taking only a month to complete one of the 328-foot vessels. In all, Charlestown built 174 large vessels during the war, including 12 barracks ships and four submarines. There were also hundreds of smaller craft, such as wooden motor launches and diver boats. The South Boston Annex played a part in the yard’s strong wartime performance, doing much of the repair and conversion work and fabricating hull sections that were towed to Charlestown for incorporation into ships under construction. Not all vessels were built outside: in the summer of 1942, shipfitters fabricated in their shop 150 fifty-foot LCMs (Landing Craft, Mechanized)—also called “tank lighters”—for the British-American invasion of North Africa. Shipfitter John Langan remembered it as a “crash program.... We just stopped everything else and concentrated on them and delivered them for the invasion.” While this kind of rapid, assembly-line construction was Charlestown’s specialty during the war, there were other claims on the yard’s time. By late 1942 war’s reality was being brought home to Charlestown in the shape of battle-scarred ships needing quick repair. When a damaged ship arrived, it was given priority until it was ready to return to combat. There was another reason for the air of urgency around war repairs: ship repair generally called for more skill than did shipbuilding. Because workers often had to work blind on battle damage until its nature and extent could be determined, such work called on all the workers’ resourcefulness. John Langan remembered “everybody fighting to get them [war-damaged vessels], because it is good work.” Langan recalled one vessel towed into the yard: it had been “torpedoed and cut right in halves ... and the fireroom was open to the seas ... [They had] tied her down with big I-beams ... tied them the full length, all the way around”—to keep the ship afloat until it reached the yard.