Nine Men’s Morris: Rules and Strategy

The three phases

Placing. Players take turns placing one piece on any empty point until all eighteen are placed. Making a mill (three of your pieces in a straight line along a board line, not across the corners of a square) during placing takes a piece just as it does later.

Moving. Once all pieces are placed, a turn is sliding one of your pieces along a line to the next empty point. Every new mill takes a piece. A mill that is opened (one piece moved out) and closed again (the piece moved back) counts as a new mill.

Flying. A player reduced to three pieces may move a piece to any empty point instead of sliding. This is a lifeline: a flying player can threaten a mill almost every move.

Taking pieces

When you make a mill you remove one enemy piece of your choice, except that pieces in an enemy mill are protected while the opponent has any piece outside a mill. If every enemy piece is in a mill, you may take from a mill.

A player with only two pieces left, or with no legal move on their turn, loses. A hundred moves without a mill is a draw.

Placing strategy

The placing phase decides most games between players who know the moving phase. Aims:

• Take junction points. The four points in the middle of the middle square's sides are the only ones with four neighbours; the corner points have two. Pieces on junctions can move and can join more lines.
• Spread out. A clump of pieces makes one mill at most; pieces spread across the board threaten several.
• Build double threats. Two pieces on one line and two on another that share an empty point: whichever the opponent blocks, you complete the other.
• Do not rush mills. A mill made in placing takes a piece but often leaves your three pieces stuck in a line. It is sometimes better to place for mobility and make the mill in the moving phase, when a running mill is possible.

The running mill

The strongest structure in the moving phase: a mill with an adjacent empty point and a piece that can slide out of the mill and back in. Open it one turn, close it the next, and take a piece every two moves. Set it up by making a mill where one of its pieces has a free neighbouring point that the opponent cannot block, and guard that point. Conversely, when the opponent has a mill, make sure every point next to it is occupied or watched, so that opening it is impossible or costly.

A double mill (two mills sharing a piece that shuttles between them) takes a piece every single move and is almost always decisive.

Mobility

In the moving phase, a player who cannot move loses. Block the opponent's pieces against the edges and corners, where they have few exits, and keep your own pieces where they have room. When choosing which enemy piece to take, take the one that could join a mill soon or the one that keeps their position mobile, not the one that is already stuck.

Flying

Down to three pieces, you can fly to any empty point, so you are dangerous: keep two pieces in line and threaten to complete the mill every turn, forcing the opponent to block rather than attack. The opponent, with more pieces, should aim to make a mill of their own as quickly as possible, since taking your fourth piece down to two ends the game.

Common mistakes

1. Placing in corners. Corners have two exits and join two lines; junctions are better.
2. Making an early mill that freezes three pieces. Mobility first.
3. Letting the opponent get a running mill. Guard the points next to any mill they make.
4. Taking the wrong piece. Take the piece that matters for the next mill, not the nearest.
5. Forgetting flying. A player on three pieces can jump anywhere; block lines, not neighbours.

Glossary

• Mill: three pieces in a line along a board line; takes an enemy piece.
• Junction point: a point with four neighbours, in the middle of the middle square's sides.
• Running mill: a mill opened and closed on alternate turns.
• Double mill: two mills sharing a piece, so that each move makes a mill.
• Flying: moving to any empty point, allowed with three pieces left.