saw the use of the heaviest and most powerful individual siege engines ever to be used: the German 800mm railway gun and the 600mm siege mortar. Though a single shell could have disastrous local effect, the guns were susceptible to air attack in addition to being slow to move. Airbridge Throughout the war both the Western Allies and the Germans tried to supply forces besieged behind enemy lines with ad-hoc airbridges. Sometimes these attempts failed, as happened to the besieged German Sixth Army the siege of Stalingrad, and sometimes they succeeded as happened during the Battle of the Admin Box (5 – 23 February 1944) and, during the short Siege of Bastogne (December 1944). The logistics of strategic airbridge operations were developed by the Americans flying military transport aircraft from India to China over the Hump (1942–1945), to resupply the Chinese war effort of Chiang Kai-shek, and to the USAAF XX Bomber Command (during Operation Matterhorn). Tactical airbridge methods were developed and, as planned, used extensively for supplying the Chindits during Operation Thursday (February – May 1944). The Chindits a specially trained division of the British and Indian armies were flown deep behind Japanese front lines in the South-East Asian theatre to jungle clearings in Burma where they set up fortified airheads from which they sailed out to attack Japanese lines of communications, while defending the bases from Japanese counterattacks. The bases were re-supplied by air with casualties flown out by returning aircraft. When the Japanese attacked in strength the Chindits abandoned the bases and either moved to new bases, or back to Allied lines. Post-World War II Several times during the Cold War the western powers had to use their airbridge expertise. The Berlin Blockade from June 1948 to September 1949, the Western Powers flew over 200,000 flights, providing to West Berlin up to 8,893 tons of necessities each day. Airbridge was used extensively during the siege of Dien Bien Phu during the First Indochina War, but failed to prevent its fall to the Việt Minh in 1954. In the next Vietnam War, airbridge proved crucial during the siege of the American base at Khe Sanh in 1968. The resupply it provided kept the North Vietnamese Army from capturing the base. In both Vietnamese cases, the Viet Minh and NLF were able to cut off the opposing army by capturing the surrounding rugged terrain. At Dien Bien Phu, the