Junkers Ju 87 of 500 sorties per day and caused heavy losses among Soviet forces, losing an average of only one Stuka per day. The Battle of Stalingrad marked the high point in the fortunes of the Junkers Ju 87 Stuka. As the strength of the Soviet Air Forces grew, they gradually wrested control of the skies from the Luftwaffe. From this point onward, Stuka losses increased. The Stuka was also heavily involved in Operation Citadel, the Battle of Kursk. The Luftwaffe committed I, II, III./St.G 1 and III./StG 3 under the command of Luftflotte 6. I., II, III. of StGs 2 and
Hugo Junkers in Dessau. The iron wings were patented one year later. Junkers had a wind tunnel built and invented a hydraulic brake. He had far-sighted ideas of metal aeroplanes and flying wings, but the necessities of the war held him back. During World War I, the government forced him to focus on aircraft production. In 1915, he developed the world's first practical all-metal aircraft design, the Junkers J 1 "Blechesel" (Sheetmetal Donkey), which survived on display in Deutsches Museum in Munich until World War II. His firm's first military production design in 1916–17 was the armored-fuselage, two-seat, all-metal sesquiplane known by