Mills(Nine Men's Morris) is an abstract strategy board game for two players that emerged from the Roman Empire. Each player has nine pieces, or "men", which move among the board's twenty-four spots. The object of the game is to leave the opposing player with fewer than three pieces or no legal moves. The game begins with an empty board. Players take turns placing their pieces on empty spots. If a player is able to form a straight row of three pieces along one of the board's lines (i.e. not diagonally), he has a "mill" and may remove one of his opponent's pieces from the board; removed pieces may not be placed again. Players must remove any other pieces first before removing a piece from a formed mill. Once all eighteen pieces have been used, players take turns moving. To move, a player slides one of his pieces along a board line to an empty adjacent spot. If he cannot do so, he has lost the game. As in the placement stage, a player who aligns three of his pieces on a board line has a mill and may remove one of his opponent's pieces, avoiding the removal of pieces in mills if at all possible. Any player reduced to two pieces is unable to remove any more opposing pieces and thus loses the game. Once a player is reduced to three pieces, his pieces may "fly" to any empty spots, not only adjacent ones.