''Call of Duty'' places the player in control of an infantry soldier who makes use of various authentic World War II firearms in combat. Each mission features a series of objectives that are marked on the heads-up displays compass the player must complete all objectives to advance to the next mission. The player can save and load at any time, rather than the checkpoint system utilized in later Call of Dutyngames.
The player has two primary weapon slots, a handgun slot, and can carry up to ten grenades. Weapons may be exchanged with those found on the battlefield dropped by dead soldiers. Unlike later Call of Duty games, the first allows the player to toggle between different firing modes (single shot or automatic fire). Call of Duty was one of the early first-person shooters to feature iron sights in game play; by pressing the corresponding key the player aims down the gun's actual sights for increased accuracy. In addition to weapons carried by the player, mounted machine gun s and other fixed weapon emplacements are controllable by the player.
The game uses a standard health points system, with a limited amount of health reflected by a health bar. Medkit s scattered throughout the levels or dropped by some foes are used to restore health when the player is injured.Call of Duty also featured shellshock not to be confused with the psychological condition of the Combat stress reaction|same name when there is an explosion near the player, he momentarily experiences simulatedtinnitus appropriate sound muffling effects, blurred vision, and also results in the player slowing down, unable to sprint.
As the focus of the game is on simulation of the actual battlefield, the gameplay differed from many single-player shooters of the time. The player moves in conjunction with allied soldiers rather than alone; allied soldiers will assist the player in defeating enemy soldiers and advancing; however, the player is given charge of completing certain objectives. The game places heavy emphasis on usage of cover suppressive fire and grenades. AI-controlled soldiers will take cover behind walls, barricades, and other obstacles when available.