The Messerschmitt Bf 109 was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid-1930s. It was one of the first true modern fighters of the era, including such features as all-metal monocoque construction, a closed canopy, a retractable landing gear, and was powered by a liquid-cooled, inverted-V12 aero engine. The Bf 109 saw active service in many air forces and was active in several conflicts outside of World War II.