What this game is
Nine Men's Morris is about lining up three pieces and taking an opponent apart one piece at a time. It is won not by speed but by still having something left at the end.
A game passes through three ages. First both sides place pieces on an empty board and size each other up. Then the pieces start crawling along the lines and every move is a choice between strengthening your own line and spoiling the other one. And when a side is down to three pieces they begin to fly anywhere on the board — the losing side suddenly revives.
Rules
- The board is three nested squares joined by lines: 24 points. There are no diagonals, so you never move corner to corner.
- Each side has nine pieces. You play blue and move first.
- Phase one. Players take turns placing pieces on any free points until all eighteen are down.
- Phase two. A piece slides along a line to an adjacent empty point. No jumping, no diagonals.
- A mill is three of your pieces on one line. Closing a mill, in any phase, lets you take one enemy piece off the board.
- You may not take a piece out of an enemy mill while that player still has pieces outside mills. If every enemy piece sits in a mill, the restriction lifts and any piece may be taken.
- A mill may be broken and closed again: every new closure earns another capture.
- Phase three. The moment a player is down to exactly three pieces, those pieces may fly to any free point on the board.
- You lose when you are reduced to two pieces, or when you have no legal move at all.
- The game is drawn when the same position appears three times, or after fifty moves without a new mill.
How to play better
- Take the busy points. A midpoint of a side belongs to two mills and connects to four neighbours, which makes it worth more than a quiet corner.
- Build a double mill: two lines sharing one piece. You shuttle that piece back and forth, closing a mill every single move and taking a piece each time. It is the fastest way to win.
- Do not rush to close a mill in phase one if it costs you the freedom to place well. A mill in a dead corner is worth less than a good shape.
- When you capture, take the piece that blocks your next mill or completes theirs — never a random one.
- Watch mobility: you can win without taking the last pieces, simply by penning your opponent in so that nothing can move.
- Do not hope to be saved by flying. Freedom of movement does not make up for lost material if the opponent has a double mill running.
A bit of history
Nine Men's Morris is among the oldest board games still played in almost its original form. Its boards turn up scratched into stone and paving across Europe and the Near East; it was played in the Roman Empire and stayed a mass pastime through the Middle Ages, with boards cut straight into benches and window ledges, monasteries and cathedrals included. Shakespeare mentions it in A Midsummer Night's Dream as an ordinary village amusement: the board was marked out on the ground, and a wet summer left it filled with mud.
In 1993 the game was solved outright — Ralph Gasser, working in Zurich, showed that faultless play by both sides ends in a draw. That put Nine Men's Morris on the short list of fully solved games alongside English draughts and Connect Four.
This is the one game on the site that was not in the 2005 collection. It was added later to fill an empty niche: a board where pieces do not capture each other but are removed one at a time for a completed line.
About the levels
Easy looks two plies ahead. It sees only piece counts and mills already closed, so a double mill catches it out every time: a line with two of your pieces and a gap simply does not register.
Hard searches six plies within about 0.4 seconds. Beyond pieces and mills it counts near-mills — lines where it already has two pieces and the third point is empty — and mobility. It is harder to beat, but it does not know that the placement phase needs a different yardstick from the endgame.
Expert goes up to sixteen plies as long as it stays inside 0.7 seconds, remembers positions it has already evaluated, and judges the board differently by phase: during placement it values blocking, in the middle mobility, in the endgame raw material. It also tracks repetition and will steer into a draw on purpose when it stands worse.