Nine Men's Morris (also called Mill, Merels, Mulino, Moulin or Mühle)
is a classic two-player strategy board game.
Objective
Reduce your opponent to fewer than 3 pieces, or leave them with
no legal moves.
Components
A board with 24 intersecting points arranged in three concentric
squares connected by lines.
9 pieces per player, white and black.
7 +--------+--------+
| | |
6 | +-----+-----+ |
| | | | |
5 | | +--+--+ | |
| | | | | |
4 +--+--+ +--+--+
| | | | | |
3 | | +--+--+ | |
| | | | |
2 | +-----+-----+ |
| | |
1 +--------+--------+
a b c d e f g
Each point is identified by a column letter (a to g) and a row number
(1 to 7). Only the 24 points where lines meet exist. The three points
a7, d7 and g7, for example, form a mill.
Phase 1 – Placing Pieces
White places first; then players alternate placing one piece
per turn onto any empty point.
Each time you form a mill (3 of your pieces in a row along a
line), you must remove one of your opponent's pieces from the
board.
Closing two mills at once with a single piece still removes only
one piece.
You cannot remove a piece that is part of a mill
unless no other pieces are available.
Optional rule (agree before playing): if all of your
opponent's pieces are part of mills, no piece is removed and the
turn simply passes to your opponent.
Phase 2 – Moving Pieces
Once all 18 pieces are placed, players alternate sliding one
piece at a time to an adjacent empty point along a line.
Forming a mill still requires you to remove an opponent's piece
(same removal rules as above).
A mill can be broken and reformed to repeatedly capture
pieces.
Phase 3 – Flying
A player reduced to exactly 3 pieces may jump their
pieces to any empty point on the board (not just adjacent
ones).
This is optional in some rule sets — confirm before playing.
Losing Conditions
A player loses if reduced to fewer than 3 pieces, or if
no legal moves are left.
Draw
The game ends immediately in a draw when the same position occurs
for the third time: the same pieces on the same points and the same
player to move. Repetitions are only counted once all pieces have been
placed. The repetitions do not need to be consecutive.
The Options page selects whether flying is allowed and how a mill is
handled when every opponent piece stands in a mill.
Copyright (c) 2016-2026 @authorOliver Merkel, Merkel(dot) Oliver(at) web(dot) de.
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Mulino implements Nine Men's Morris, a two-player deterministic
board game.
The computer player uses Monte-Carlo Tree Search (MCTS) with UCB
(Upper Confidence Bounds) applied to trees (UCT in short). The board game
is used for demonstration purposes of the UCT algorithm.
The traditional Nine Men's Morris game belongs to the public domain due
to its age and unknown author and/or creator.
