The Mikoyan i Gurevich MiG-21 has been built in greater numbers than any other combat aircraft since 1945. It also saw service with more air forces than any other type manufactured over the last 70 years. Locally designated the 'L' (for Lovac or fighter), for more than half a century over 260 MiG-21s in 12 different versions and sub-variants formed the backbone of the Yugoslav Air Force and Air Defense Force (JRV i PVO) and later the Serbian Air Force (RV i PVO). Entering service at the peak of the Cold War, the MiG-21 quickly replaced the US-supplied North American F-86E and F-86D Sabres in the Yugoslav inventory. The first version, MiG-21F-13, was followed by the MiG-21PFM in 1967, and MiG-21M/MF in 1970. Serving with the 204th Fighter Regiment, the task of these fighters was the air defense of Belgrade, capital of Yugoslavia.