Willy Messerschmitt began his work on this deadly aircraft in 1935, in response to Germany's proposed need for a New modern Monoplane, or a plane with one pair of wings. It was later revealed in September, 1935, when the first of 13 prototypes first flew. It later entered service in 1937, and saw it's first form of combat during the Spanish Civil War, with two different Variants seeing combat during the war. They were later followed by two more versions in 1938, the Bf109D, and the Bf109E, or "Emil". These later two versions were Germany's standard fighter at the start of WWII, being well successful in their combat scenes over Poland, Scandinavia, and the low countries. It's limitations were first realized by the Luftwaffe during the Battle of Britain, and was followed by many different variants. The most numerous variant was the Bf 109(G), but few pointed out the poorer qualities of handling.