In many ways, WWII was the beginning of unbridled mechanized combat — and the development of Hitler's Gustav gun only added to that legacy. The Gustav arm was like nothing else anyone had ever seen before: At a whopping four-stories high and weighing in at over 1,350 tons, the giant tank-like machine had destructive abilities that put it in a class of its own. But it did have its downsides.
The giant device was hugely impractical and was not at all subtle in the German countryside, leaving its operators incredibly vulnerable to storm from Allied planes overhead — not to mention the fact that the arm could only be fired 14 times a day based on the tedious nature of its operation.
Despite the fact that only two of these were ever manufactured, and that they were sent to the junk yard within a year, the Gustav remains one of the most devastatingly impressive methods of firepower ever developed, and without a doubt one of the largest.
Near the beginning of WWII, Germany set its sights on overtaking its western neighbor, France. France's military defenses relied on rather archaic methods recycled from WWI, so Germany decided to get creative.
France's only real defense against the Third Reich's army was its Maginot Line, which was essentially "a great line of fortifications that spanned France's borders with several neighbors," forming, "a glorified trench." And despite the fact that the line itself was strongest along France's boarder with Germany, it was naively outdated when it came to the mechanized fighting that was ushered in by WWII.
Though Hitler eventually had his armies simply bypass the Maginot Line, he still continued the development of the device that would have allowed him to end the line altogether.
The creation of the Gustav began with Hitler employing the expertise of the Friedrich Krupp A.G. company out of Essen, Germany, with the intent of developing a railway gun capable of devastating the French trench. The result was a four-story, 1,350-ton gun that was capable of firing off both 10,000-pound shells and "16,540-pound concrete-piercing shells — roughly the weight of an unladen 71-passenger school bus, traveling at 2700ft/s."
The device's precision was also remarkably high — it could hit a target as far as 29 miles away and could break through as much as 264 feet of reinforced concrete with a single blow.
The Gustav and its sister machine, the Dora, only saw brief action. In total, the Gustav fired off a little over 300 rounds in its lifetime before its bulky self was seized by the Allies. Dora's fared no better: The Germans quickly dismantled it for fear of it being taken and used against them.
The failure of the device within just a year's time can be credited to both its enormously impractical size as well as its slow recovery time. The Gustav not only had to be transported from place to place via railway, but was so large that it had to be partially disassembled as well, adding to the time required to simply get it into firing position. Once it was ready to go, it would only end up being able to fire around 14 rounds per day, thanks to how involved the process of loading it was. Plus, it could hardly be considered stealthy and was particularly vulnerable to Allied war planes.