War is also a simple card game
The game is usually between two people (any more than three and the game becomes difficult), who each have a full deck of cards.
Each player turns over the top card on their pile at the same time. The player with the highest card wins the other player's card. (The card with the lowest value is 2 and the greatest is an ace.) If both players have a card of equal value, then the next card is shown until someone has a card larger than everyone elses.
Repeat until someone runs out of cards, then count all of the cards won by each side. The player with the highest number of cards wins the war.