In the game of War, both players flip the top card of their deck and compare them. Whoever has the higher card wins the round and keeps both cards, adding them to the bottom of their deck. Aces are considered higher than all cards 3-K and smaller than 2s. If a round is tied, the cards are placed in a loot pile along with the next three cards from each player's deck, and the winner of the next round wins all of the loot.

War is a simple game. In fact, there is no user decision making or input that determines the result of the program; the game's outcome is entirely deterministic and is always a result of the initial shuffle. Thus, the controls for the program are simple: the user will repeatedly press "enter" to progress to the next phase of the simulation until the simulation is complete.

When the simulation is finished (aka when one player runs out of cards), the screen displays the winner and the game ends.