The X class was a World War II midget submarine class built for the Royal Navy during 1943–44. Known individually as X-Craft, the vessels were designed to be towed to their intended area of operations by a full-size 'mother' submarine - (usually one of the T class or S class) - with a passage crew on board, the operational crew being transferred from the towing submarine to the X-Craft by dinghy when the operational area was reached, the passage crew returning with the dinghy to the towing submarine. Once the attack was over, the X-Craft would rendezvous with the towing submarine and then be towed home. Range was limited primarily by the endurance and determination of their crews, but was thought to be up to 14 days in the craft or 1,500 miles (2,400 km) distance after suitable training. A