long-range bombardment role. Nevertheless, the Germans built a handful of powerful Krupp K5s and the largest artillery pieces (by caliber) ever used in combat: the 800 mm (31.5 in.) Schwerer Gustav and Dora. The latter had been designed specifically to defeat the Maginot Line, firing a 7-ton shell to a range of . Although their original role proved unnecessary, Gustav was used successfully to destroy Soviet heavy fortifications, most notably those at Sevastopol. Dora was readied for combat at Stalingrad, but was withdrawn before it could be used. Development might have continued but for the ever-increasing Allied air power, which limited Hitler's options in terms of re-opening bombing attacks on London. This led to the development of the V-3 "London Gun" or "Hochdruckpumpe", fired from Mimoyecques in the Pas de Calais, about away. Two attempts to build underground bunkers for the huge weapons were thwarted by massive Royal Air Force bombing raids, which made further attempts futile. Two smaller prototype versions of the gun were used during the Battle of the Bulge. During World War II, the British developed an experimental 13.5/8 inch hypervelocity gun named Bruce, which was deployed near St Margaret's in Kent among their cross-Channel guns. It was intended only for stratospheric experiments, primarily with smoke shells. These experiments were important in the development of the Grand Slam bomb. It was used from March 1943 through February 1945. The "Supergun Affair" Canadian engineer Gerald Bull became interested in the possibility of using 'superguns' in place of rockets to insert payloads into orbit. He lobbied for the start of Project HARP to investigate this concept in the 1960s, using paired ex-US Navy 16"/50 caliber Mark 7 gun barrels welded end-to-end. Three of these 16"/50 (406 mm) guns were emplaced, one in Quebec, Canada, another in Barbados, and the third near Yuma, Arizona. HARP was later cancelled, and Bull turned to military designs, eventually developing the GC-45 howitzer. Some years later, Bull interested Saddam Hussein in funding Project Babylon. The objective of this project is not certain, but one possibility is that it was intended to develop a gun capable of firing an object into orbit, whence it could then drop onto any place on the Earth. Gerald Bull was assassinated in March 1990, terminating development, and the parts were confiscated by British customs after the Gulf War. It has been suggested that the US Navy had developed a