Nine men's morris

How a game runs

The board is three squares, one inside the other, joined at the middle of each side. That gives twenty-four points and sixteen possible mills. Both players start with nine men in hand; Light moves first.

In the placement phase you put one man per turn on any empty point. Three of your men on one straight line form a mill, and closing a mill lets you remove one enemy man. A man that stands in a mill is protected unless every enemy man is in a mill. Closing two mills with a single move still takes only one man.

When all eighteen men are down, the movement phase begins: a turn means sliding one man along a line to a neighbouring empty point. Opening a mill and shutting it again on a later turn is the usual way to keep taking men.

A player reduced to three men may fly: those men jump to any empty point. The game is lost by the player who is left with two men or has no legal move. Three repetitions of a position, or a hundred turns in a row without a capture, end the game as a draw.

Habits that win games

• Value the four junction points d2, b4, f4 and d6. Each touches four lines, while a corner touches only two.
• Count free moves, not men. A side with nine men that cannot move has lost; plan the end of placement so your men still have room.
• Look for the fork: one man that completes two different twos at once. The opponent can block only one of them.
• Aim for a swing mill, where one man slides back and forth between two mills and closes one of them every turn. Against that formation the opponent bleeds a man per move.
• Keep a man in hand for defence late in placement. The last placements decide whether your opponent can still close the mill you see coming.

Mistakes that cost the game

• Grabbing the first possible mill. Three men stuck on an outer side can be locked in place, and the man you took is soon paid back with interest.
• Filling corners early. They have only two neighbours and are the first points to be blocked.
• Forgetting the opponent's two-in-a-line during placement. When he has two open twos at once, one of them closes.
• Removing a man at random. Take the one that breaks a future mill or frees your blocked men, not the nearest.

Playing the computer here

Novice misses tactics and lets you practise forks. Squire looks a few moves ahead. Knight punishes loose men. Champion searches as deep as its clock allows and rarely lets a mill threat slip. Undo takes back your move together with the reply, and Hint shows the move the Champion would choose.