The Messerschmitt Bf.109 was one of the first truly modern fighters of WWII. Originally conceived as an interceptor, the Bf.109 fulfilled multiple roles, as bomber escort, fighter-bomber, ground-attack aircraft, and reconnaissance aircraft. The final production version of the Bf.109 was the K series, or "Kurfurst." Externally similar to the G series, it had a large number of internal and aerodynamic changes that improved its effectiveness and remedied existing flaws, which kept it competitive against rival fighters.