Schwerer Gustav was a German 80-centimetre (31.5 in) railway gun. It was developed in the late 1930s by Krupp in Rügenwalde as siege artillery for the explicit purpose of destroying the main forts of the French Maginot Line, the strongest fortifications in existence at the time. The fully assembled gun weighed nearly 1,350 tonnes and could fire shells weighing 7t to a range of 47 km.

Dora (after the wife of the chief engineer) was the second gun produced. The gun was required to 'pierce a metre or steel, 7 metres of concrete, or 30 metres of dense earth' and was so enormous two parallel railway tracks were necessary to ensure stability and weight distribution. Gun weight 1344 tonnes, barrel weight 400 tonnes, shell weight 7100kg. Range 40km, max elevation 53°, overall length 43m. It was deployed briefly against Stalingrad, where the gun arrived at its emplacement 15 kilometres west of the city sometime in mid-August 1942. It was ready to fire on 13 September. It was withdrawn when Soviet forces threatened to encircle the German forces. When the Germans began their long retreat, they took Dora with them.