The setting itself and the scale of the conflict also result in a very different map (not just because it only covers North and Central America instead of the whole world).
Many of the game systems have been overhauled to better reflect the post-apocalypse nature of the setting. Not only that, every major faction has options that the player can take to radically alter their directions, like turning Caesar's Legion into an actual nation-state or turning the NCR into an oligarchic dictatorship in all but name. The player can play as any of the West Coast factions in addition to a plethora of original ones. Old World Blues is a popular Hearts of Iron IV Game Mod set in the Fallout universe, or rather, an alternate universe version of it.
