An American sailor works on the propeller of a torpedo in the storage locker of Task Unit 122.4.4 (formerly Task Group 122.9). Both Mark 13 and Mark 8 torpedoes, the principal armament of PT Boats during World War II, are on the rack. The Mark 8 torpedo was designed and built by Bliss-Leavitt Corporation and entered service in 1911. The first 21 inch (533 mm) torpedo, it was originally employed on World War I-era destroyers; some 600 examples were sent to Britain with the fifty outmoded "four-piper" destroyers in 1940. The Mark 13 was developed in 1935 as an air-dropped torpedo and had reinforced gyroscopes compared to the Mark 8. By World War II, the Mark 8 was adapted to serve on PT Boats in the Pacific and European Theatres. It suffered from poor exploders and mechanical unreliability. In addition, in the event of a misfire by the compressed air tube, a sailor would strike a gunpowder charge with a sledgehammer to launch the torpedo; the resulting explosion was very bright and revealed the PT Boat's position. The lighter Mark 13 could be dropped off the PT Boat instead of fired through a compressed air tube, reducing the need for tubes and complicated firing gear. After a long teething period, the Mark 13 was a deadly air-dropped torpedo, but also had flaws as a PT weapon. At a cost of $40 million, all Mark 8s and other obsolete torpedoes, some 4,300 units, were scrapped in 1945; some sailors were upset because they had maintained these torpedoes for decades. Task Unit 122.4.4 was the designation for all American PT Boats during the Normandy invasion. Four squadrons, led by United States Navy Commander John D. Bulkeley, conducted patrols, countered German E-boats, and escorted the invasion fleet to Normandy. MTB squadron 2, the smallest PT Boat squadron in the war, operated four boats in special operations for the Office of Strategic Services. These missions were unpopular not only because the constant need for stealth wore down nerves, but often the missions made no sense to the crews. One operation collected sand from Omaha Beach, but the crews had no way of knowing that they were testing the beach for tanks. This photo, part of a series taken by the Office of Strategic Services Field Photography Unit run by United States Navy Commander John Ford, may have been background for his first commercial film after leaving the OSS. They Were Expendable was released after the war ended in December 1945. The film told the story of Bulkeley's operations during the Japanese invasion of the Philippines in early 1942.