The Makarov pistol resulted from a design competition for replacing the Tokarev TT-33 semi-automatic pistol and the Nagant M1895 revolver. Rather than building a pistol to an existing cartridge in the Soviet inventory, Nikolai Makarov took up the German wartime Walther 'Ultra' design, fundamentally an enlarged Walter PP, utilizing the 9x18mm Makarov cartridge designed by B.V. Semin in 1946. For simplicity and economy, the Makarov pistol was of straight blowback operation, with the 9x18mm Makarov cartridge being the most powerful cartridge it could safely fire. The Luftwaffe had rejected this pistol design some years before because of its poor accuracy. Although the nominal calibre was 9.0mm, the actual bullet was 9.22mm in diameter, being shorter and wider and thus incompatible with pistols chambered for 9x19mm Parabellum cartridges. Consequently, Soviet ammunition was unusable in NATO firearms and, in the event of war, NATO forces would be unable to use ammunition from Soviet sources.