in large numbers through lend-lease. Four hundred of the 3,600 Horsas built were supplied to the USAAF. The most famous British actions using gliders included the unsuccessful Operation Freshman, against a German heavy water plant in Norway in 1942; and the capture of the Caen canal and Orne river bridges in a coup-de-main operation at the very start of the invasion of Normandy. Other glider actions included Operation Dragoon (the invasion of southern France), Operation Market Garden (the landing at Arnhem Bridge to try and seize a bridgehead over the lower Rhine) and Operation Varsity (crossing of the Rhine). Out of the 2,596 gliders dispatched for Operation Market Garden, 2,239 were effective in delivering men and equipment to their designated landing zones. Although gliders are still used in the Royal Air Force in the Royal Air Force Gliding & Soaring Association and for cadet training by the Air Training Corps, they are not used in combat operations. No troop-carrying gliders have been in British service since 1957. American military gliders United States Army, Army Air Forces, and Air Force Major General Henry "Hap" Arnold, Acting Deputy Chief of Staff for Air (becoming Commanding General of the United States Army Air Forces on March 9, 1942), initiated a study with view to develop a glider capable of being towed by aircraft. This directive was set into motion through Classified Technical Instructions (CTI-198 on 24 February 1941, and CTI-203 on 4 March 1941), which authorized the procurement of 2-, 8-, and 15-place gliders and equipment. Eleven companies were invited to participate in the experimental glider program, but only four responded with any interest, Frankfort Sailplane Company (XCG-1, XCG-2), Waco Aircraft Company (XCG-3, XCG-4), St. Louis Aircraft Corp. (XCG-5, XCG-6), and Bowlus Sailplanes (XCG-7, XCG-8). Only Waco Aircraft Company was able to deliver the experimental glider prototypes that satisfied the requirements of Materiel Command, the eight-seat Waco CG-3 (modified to become a production nine-seat glider) and the fifteen-seat Waco CG-4. In October 1941, Lewin B. Barringer was made Glider Specialist, Air Staff, HQ of the Army Air Forces, answering to General Arnold, and placed in charge of the glider program. The shock of the Japanese attack on Pearl Harbor on 7 December 1941 prompted the United States to set the number of glider pilots needed at 1,000 to fly 500 eight-seat gliders and 500 fifteen-seat gliders. The number of pilots required was increased