The navy and air force also require men and equipment, including the actual warships and warplanes that are used in combat. These divisions require equipment and manpower to fight properly. For the ground forces, the player may train, customize, and command divisions consisting of various types of infantry, tanks, and other units. A nation's military is divided between naval forces, aerial forces, and ground forces. The player may play as any nation in the world in the 1936 or 1939 start dates in single-player or multiplayer, although the game is not designed to go beyond 1948.

Hearts of Iron IV is a grand strategy wargame that primarily revolves around World War II.