Nine Men's Morris is a strategy board game for two players dating at least to the Roman Empire.

Rules

The board consists of a grid with twenty-four intersections or points. Each player has nine pieces, or "men". Players try to form 'mills'—three of their own men lined horizontally or vertically—allowing a player to remove an opponent's man from the game.
A player wins by reducing the opponent to two pieces (where he could no longer form mills and thus be unable to win), or by leaving him without a legal move.

Strategy

At the beginning of the game, it is more important to place pieces in versatile locations rather than to try to form mills immediately and make the mistake of concentrating one's pieces in one area of the board. An ideal position, which typically results in a win, allows a player to shuttle one piece back and forth between two mills, removing a piece every turn