How to play nine men's morris
Nine men's morris is a two-player strategy game, also called the mill game, merels or Mühle. The board has 24 points on three nested squares joined at the middle of each side. Each player has nine pieces, white and black, and white moves first. Three of your pieces in a row along a line form a mill; the board has 16 possible mills. Every time you form a mill, you remove one of your opponent's pieces.
The game has three stages. Placing: players take turns putting a piece on any empty point until all eighteen are on the board. Moving: each turn you slide one piece along a line to a neighboring empty point. Flying: when a player is down to three pieces, their pieces may jump to any empty point. Flying is a common house rule and is on by default here; untick Flying to play without it.
When you form a mill you must remove an opponent piece that is not part of a mill. Only when every one of their pieces sits in a mill may you take one from a mill. You win when your opponent has only two pieces left, or when it is their turn and they cannot move. The game is a draw when the same position appears for the third time with the same player to move, or after 50 moves by each player in a row with no piece removed.
How to use this page
Tap an empty point to place a piece. Once all pieces are placed, tap one of your pieces, then the empty point to move it to; possible moves are outlined. When you close a mill, the pieces you may remove are outlined in red: tap one. With a keyboard, use the arrow keys to move between points and Enter to choose. Undo takes back your last move and the computer's reply, and New game starts again. Your game is saved in this browser.
Points are named like a chess board: columns a to g from left to right, rows 1 to 7 from the bottom. The move list writes a placement as d6, a move as d6-d5, and a removal with an x, so d6-d5xg7 means the piece moved from d6 to d5, closed a mill and removed the piece on g7.
The computer levels
- Easy closes a mill when it can, blocks your mill when you are one move from closing it, and otherwise plays at random.
- Medium looks three moves ahead (its move, yours, its next) and scores positions by pieces, mills, open twos and how freely each side can move.
- Hard uses the same scoring but searches as deep as it can in about one and a half seconds, with alpha-beta pruning and a memory of positions it has already scored. At the end of its search it keeps playing out mill closings, so it does not leave a piece hanging, and it counts a repeated position as a draw, so it presses on when it is ahead. It sets up double threats and sees most of yours. It is strong for a quick game but not perfect.
Hint runs the hard search for two seconds on your position and outlines the best move it found, with the piece to remove if it closes a mill. Choose Two players to play a friend on one device; hints still work there.
We tested the engine before publishing: on random positions every level returned a legal move, and in test positions all three levels took a mill when one was available and blocked a mill the other side was about to close. The rules code was checked move by move against a separate model of the board over 300 random games. We also played the levels against each other with the first move alternating: hard won 16 of 16 games against medium at its normal thinking time, medium won 30 of 30 against easy, and hard and easy both won 30 of 30 against random moves.
Strategy tips
- Do not rush mills while placing. The middle points of the middle square, d6, b4, f4 and d2, have four neighbors each, more than any other point, so pieces there stay mobile. A spread-out position with many possible mills is worth more than one early capture.
- Watch mobility. In the moving stage a player who cannot move loses, so crowding your opponent's pieces into corners can win without a single mill.
- Build a running mill. A piece that can slide out of a mill and back in on the next move forms the mill again every two turns, and your opponent loses a piece each time unless they block the gap.
- Count before flying. With three pieces left you can fly anywhere, so block every line where your opponent has two in a row.
Nine men's morris is one of the oldest board games still played. In 1993 the computer scientist Ralph Gasser showed that with perfect play from both sides the game ends in a draw.
For a game small enough to solve completely, see the tic tac toe solver; for a one-player board puzzle, peg solitaire.
Solver tested . Found a problem? Tell us.
Questions
How do you win nine men's morris?
Reduce your opponent to two pieces by forming mills, or leave them with no legal move on their turn. Each mill you form, three of your pieces in a row along a line, removes one of their pieces.
What is flying in nine men's morris?
When a player has only three pieces left, they may move a piece to any empty point instead of only to a neighboring one. It gives the losing side a fighting chance. Many players use it, some do not, so it is an option here, on by default.
Can you remove a piece that is in a mill?
Only if every one of your opponent's pieces is in a mill. Otherwise you must take a piece that is not part of a mill. The pieces you are allowed to remove are outlined on the board.
Is nine men's morris a draw with perfect play?
Yes. Ralph Gasser solved the game in 1993 with a computer search and showed that perfect play from both sides leads to a draw. The hard level here is a fast search, not that perfect database, so it can still be beaten.
Is the mill game the same as nine men's morris?
Yes. The mill game, Mühle in German, molenspel in Dutch and merels in old English are the same game: 24 points, nine pieces each, and three in a row removes an opponent's piece. Smaller versions such as three and six men's morris use fewer pieces and a smaller board.
How long can a game last?
The page ends a game as a draw after 50 moves by each player in a row without a piece being removed, or when the same position comes up for the third time. Most games end long before that.