mount itself would be elevation, traverse being managed by moving the weapon along a curved section of railway line. Krupp prepared plans for calibres of 70 cm, 80 cm, 85 cm, and 1 m. Nothing further happened until March 1936 when, during a visit to Essen, Adolf Hitler inquired as to the giant guns' feasibility. No definite commitment was given by Hitler, but design work began on an 80 cm model. The resulting plans were completed in early 1937 and approved. Fabrication of the first gun started in mid-1937. Technical complications in the forging of such massive pieces of steel made it apparent that the original completion date of early 1940 could not be met. Krupp built a test model in late 1939 and sent it to the Hillersleben proving ground for testing. Penetration was tested on this occasion. Firing at high elevation, the shell was able to penetrate the specified seven metres of concrete and the one metre armour plate. When the tests were completed in mid-1940 the complex carriage was further developed. Alfried Krupp, after whose father the gun was named, personally hosted Hitler at the Rügenwalde Proving Ground during the formal acceptance trials of the Gustav Gun in early 1941. Two guns were ordered. The first round was test-fired from the commissioned gun barrel on 10 September 1941 from a makeshift gun carriage at Hillersleben. In November 1941, the barrel was taken to , now Darłowo, Poland, where eight further firing tests were carried out using the 7,100 kilogram armour-piercing (AP) shell out to a range of . In combat, the gun was mounted on a specially designed chassis, supported by eight bogies on two parallel railway tracks. Each of the bogies had five axles, giving a total of 40 axles (80 wheels). Krupp named the gun Schwerer Gustav (Heavy Gustav) after the senior director of the firm, Gustav Krupp von Bohlen und Halbach. The gun could fire a heavy concrete-piercing shell and a lighter high-explosive shell. An extremely-long-range rocket projectile was also planned with a range of , that would require the barrel being extended to . In keeping with the tradition of the Krupp company, no payment was asked for the first gun. They charged seven million Reichsmark (approximately 24 million USD in 2015) for the second gun, Dora, named after the senior engineer's wife. History Schwerer Gustav In February 1942, Heavy Artillery Unit (E)