Schwerer Gustav (English: Heavy Gustaf or Great Gustaf) was the name of a German 80 cm railway gun. It was developed in the late 1930s by Krupp as siege artillery for the explicit purpose of destroying the main forts of the French Maginot Line, the strongest fortifications then in existence. The fully assembled gun weighed nearly 1,350 tonnes, and could fire shells weighing seven tonnes to a range of 47 kilometres (29 mi). The gun was designed in preparation for the Battle of France, but was not ready for action when the battle began, and in any case the Wehrmacht's Blitzkrieg offensive through Belgium rapidly outflanked and isolated the Maginot Line's static defenses, forcing them to surrender uneventfully and making their destruction unnecessary. Gustav was later employed in the Soviet Union at the siege of Sevastopol during Operation Barbarossa, where among other things, it destroyed a munitions depot buried in the bedrock under a bay. The gun was moved to Leningrad, and may have been intended to be used in the Warsaw Uprising like other German heavy siege pieces, but the rebellion was crushed before it could be prepared to fire.