Call of Duty 2: Big Red One is a first-person shooter that has a single-player story mode and a multiplayer mode. The player takes on the role of a soldier protagonist in specific missions during World War II from the perspective of the American 1st Infantry Division. The player can crouch and lie prone, and is able to scale low walls and other obstacles. Two firearms can be carried, which can be swapped with those left on the battlefield, and both fragmentation and smoke grenades can also be carried. A gun's iron sights can be used to aim more accurately. A compass on the heads-up display (HUD) shows both allies and enemies, and objective markers to indicate locations the player must reach, areas to defend, or enemy cannons or tanks that the player must plant explosives on to disable. Emplaced weapons such as machine guns and flak cannons are available in some locations to take out enemy forces. In addition, some missions place the player in control of a tank. It is also important for scouting, though most of the game takes place in personal, close combat situations reducing the importance of this tactic.