Heinkel's He 112 was a fighter aircraft designed by Walter and Siegfried Günter. It was one of four planes designed to compete for the Luftwaffe's 1933 fighter contract, which was eventually won by the Messerschmitt Bf 109. Small numbers of the He 112 were used for a short time by the Luftwaffe, and small runs were completed for several other countries, but less than one hundred were completed in total. Condor Legion When it was clear the 112 was losing the contest, Heinkel offered to re-equip the V6 prototype with 20 mm cannon armament as an experimental aircraft. The Technisches Amt was very interested; at the time many tanks were equipped with 20 mm guns as their primary anti-tank armament, the same armament on a plane could prove to be a powerful weapon. In September a 20 mm MG C/30L cannon was mounted to the plane, with the breech to the rear of the engine and the barrel lying between the cylinder banks and exiting in the propeller spinner. This is the first experimental mounting of what would later be called the Motorkanone, a feature that would become a standard on most single-inline engined German fighters. She was then broken down and shipped to Spain on 9 December. After being re-assembled she was assigned to Versuchsjagdgruppe 88, a group within the Legión Cóndor devoted to testing new planes. There she was nicknamed the Kanonenvogel, and joined three V-series Bf 109s which were also in testing. The Kanonenvogel was adopted by Oberleutnant Günter Radusch who started flying the plane on 9 December at Tablada. From then on it joined the Ju 87As and Hs 123s already in service and was used as a ground attack plane. On 6 February the plane was moved to Villa de Prado near Madrid, and then in March, she was reassigned to Jagdgruppe 88 at Almorox near Toledo. While sitting at Almorox due to a mechanical problem in his He 45C, Oberleutnant Wilhelm Balthasar heard that a Republican armored train was approaching and talked himself into the cockpit of the V6 by insisting he was a Heinkel test pilot. After teaching himself to fly the plane and managing to get into the air, he found the train parked at the station in Seseña and attacked it. On his third pass, one of the 20 mm shells punctured the ammunition car and the entire train exploded. Then