Messerschmitt Bf 109 11 July 1938 when Erhard Milch finally allowed Willy Messerschmitt to acquire the company. All Messerschmitt aircraft that originated after that date, such as the Me 210, were to carry the "Me" designation. Despite regulations by the RLM, wartime documents from Messerschmitt AG, RLM and "Luftwaffe" loss and strength reports continued to use both designations, sometimes even on the same page. All extant airframes bear the official "Bf 109" designation on their identification plates, including the final K-4 models. The aircraft was often referred to by the folk-designation, 'Me 109', particularly by the Allies. The aircraft was often nicknamed "Messer"
Luftwaffe unravel with the failure of the invasion of the Soviet Union. The "peripheral" strategy of the "Luftwaffe" between 1939 and 1940 had been to deploy its fighter defences at the edges of Axis occupied territory, with little protecting the inner depths. Moreover, the front line units in the West were complaining about the poor numbers and performance of aircraft. Units complained of lack of "Zerstörer" aircraft with all-weather capabilities and the "lack of climbing power of the Bf 109". The "Luftwaffe"s technical edge was slipping as the only formidable new aircraft in the German arsenal was the Focke-Wulf Fw 190.