Although initially hampered by the restrictions imposed by the Versailles Treaty, Germany rapidly developed a system of highly effective antiaircraft weapons. An early attempt, adopted in 1928, the 75mm FlaK38 fired a 14-pound shell to a maximum ceiling of 37,730 feet. In the decade following World War I, Krupp arranged with the Swedish arms giant Bofors to allow its engineers to work secretly on new designs in Sweden. One of the most successful artillery pieces of all time came about as a result of that arrangement— the famous German Eighty-Eight. Originally designed as an antiaircraft gun, combat experiences in the Spanish Civil War and early World War II proved the Eighty-Eight’s versatility in other applications. By war’s end, German designers had also adapted it to antitank, tank, and conventional field applications. The first test model was assembled in 1931, and after trials the new gun went into service in 1933 as the caliber 88mm FlaK18. With a veteran crew it achieved a firing rate of 15 rounds per minute. The FlaK18 fired a 21-pound shell to a maximum ceiling of 26,247 feet, and in a ground role it achieved a range of 9.2 miles.
Krupp engineers continued to improve the FlaK18 and also redesigned it to ease its manufacture. The redesigned Eighty-Eight entered service in 1937 as the Flak36 and saw considerable service with Germany’s Condor Legion in the Spanish Civil War. Having proved the gun’s effectiveness as a ground weapon in Spain, Krupp again improved the Eighty-Eight, by adding ground sights and providing high-explosive shells for field use. Firing high-explosive and armor-piercing ammunition, the Eighty-Eight further proved itself against British armor in North Africa in 1941–1942. As the war progressed, it became increasingly necessary to increase German tank armament to match the heavy guns and armor of the new Soviet tanks on the Eastern Front. That necessity resulted in slight modifications to the basic Eighty-Eight design, which resulted in the Kwk36 (Kampfwagen Kanone) and the Kwk43, for use in Tiger tanks and self-propelled guns.