Eager to invade France, Nazi leader Adolf Hitler demanded a new weapon that could easily pierce the concrete fortifications of the French Maginot Line — the only major physical barrier standing between him and the rest of Western Europe.

In 1941, the year after France fell, German steelmaker and arms manufacturer Friedrich Krupp A.G. company began constructing Hitler's Gustav gun, according to "Top Secret Weapons" documentary.

The four-story, 155-foot-long gun, which weighs 1,350 tons, shot 10,000-pound shells from its mammoth 98-foot bore.

The massive weapon was presented to the Nazis free of charge to show Krupp's contribution to the German war effort, according to historian C. Peter Chen.

In spring 1942, the Gustav gun made its debut at the siege of Sevastopol. The 31-inch gun barrel fired 300 shells on the Crimean city.

The weaponry demanded extensive resources and required a crew of 2,000 to function Business Insider (Business Insider)

As the Nazis would soon find out, however, the ostentatious gun had some serious disadvantages:

Its size made it an easy target for Allied bombers flying overhead

Its weight meant it could be transported only via a costly specialised railway (which the Nazis had to build in advance)

It required a crew of 2,000 to operate

The five-part gun took four days to assemble in the field and hours to calibrate for a single shot

It could fire only 14 rounds a day

Within a year, the Nazis discontinued the Gustav gun, and Chen notes that Allied forces eventually scrapped the massive weapon

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