Wolfenstein is a series of World War II video games originally developed by Muse Software. The majority of the games follow William "B.J." Blazkowicz, an American Army captain, and his fight against the Axis powers. Earlier titles are centered around Nazis attempting to harness supernatural and occult forces, while later games are set in an alternate history in which Axis powers won World War II. The first two games in the series, Castle Wolfenstein and Beyond Castle Wolfenstein, focused on stealth-based gameplay from a top-down perspective. Beginning with id Software's Wolfenstein 3D, they shifted to, and helped popularize, the first-person shooter genre. After ZeniMax Media acquired id Software, including the Wolfenstein franchise, developer MachineGames became the series' primary developer.