A complete guide: placing nine pieces, how to close mills and capture the opponent's pieces, the moving and flying phases, controls on muta.pro and tactics for beginners.
Nine Men's Morris is a duel on a board of three nested squares with intersection points. Each player controls nine pieces. By closing three of your pieces into a single row — that is a mill — you remove one of the opponent's pieces from the board. The game is won when the opponent has two pieces left (a mill can no longer be formed from them) or when they have no move to make.
The board is empty and each side holds 9 pieces. You play red and move first; blue is controlled by the opponent or the bot. Play alternates and passes through three phases: placing, moving and flying. On muta.pro the current phase, whose turn it is, and how many pieces each side has on the board and in reserve are shown on the side panel.
First the players take turns placing their pieces on any empty points. This takes up each player's first nine moves — until all 18 pieces are on the board.
Three of your pieces in one straight row form a mill. Complete a row and you immediately remove one of the opponent's pieces. This works both while placing and while moving.
By the rules you cannot take a piece that stands inside a mill — as long as free ones are available. But once all of the opponent's pieces are locked in mills, you may take any of them.
Once your supply runs out, on your turn move one piece to an adjacent empty point along a line. Open and close mills again to keep capturing pieces.
As soon as a player is down to exactly three pieces, flying kicks in for them: their pieces may be placed on any empty point on the board, regardless of adjacency.
The strongest tactic is two mills sharing a common point: by moving a piece away you open one and immediately close the other, capturing an opponent's piece every turn.
Victory is recorded automatically on one of two conditions. First — the opponent is down to two pieces: they can no longer form a new mill. Second — the opponent has no move at all (all their pieces are locked and the game is past the placing phase). In both cases muta.pro declares the winner at once. Pieces can only be captured with a mill, so there are no points as such — what matters is the piece advantage and control of the intersections.
Points where lines cross belong to several rows at once — mills are easier to build from them.
Place your pieces so that a single move opens one mill and closes an adjacent one. It is a piece-eating machine.
Closing three pieces and only moving them around is a dead end. Build a pair of set-ups at once.
See two of the opponent's pieces adjacent with a free point — close it and deny them the mill.
There are 24 points on the board, but they are not equal. The four midpoints of the central square's sides are four-way intersections: four lines run from each, and the point belongs to two potential mills at once. Corner points give only two connections. Spend your first placing moves precisely on the four-way centres — double threats and running mills grow from them.
The early stage is not a race for the first mill but the weaving of a network. The ideal is a piece that "looks at" two unfinished rows at once. Then you create a double threat: the opponent cannot close both rows in one move, and one mill is guaranteed to close. A single row is simply blocked by an experienced player one move before it closes. A practical benchmark: by mid-placement hold not a finished mill but two or three "half-mills", each threatening to close — then the initiative is always yours.
Double threat: both golden points complete a mill — the opponent can close only one.
The four middle points give four connections each. Take two or three and you control more than half the board's lines before it even fills up.
Be glad not of a finished mill but of a position where you threaten two rows at once. One threat gets closed; two in one move cannot be.
An early mill often freezes three pieces in a dead end. Save the close for the moment the opponent's supply has run out.
A running mill is two mills with a shared piece at the junction: move it one step and you dismantle one mill, move it back and you close it again and capture a piece. If a second pairing stands nearby, the piece swings back and forth and eats one piece every turn. It is the most lethal mechanism in the game — the whole middle game turns on who assembles a running mill first.
The classic set-up is the "fir tree": two parallel unfinished rows with a shuttle darting between them. From the moment it launches, the opponent has exactly one move to save themselves. There are three ways to break an opponent's running mill: occupy the pivot point in advance; step onto the return square during the single move when it is open; or build a counter running mill and trade piece for piece. Remember: an opened mill captures a piece only when it closes again, so a running mill lives exactly as long as the return square is free — the whole counterplay comes down to the fight for that one point.
Running mill: the shuttle (gold) swings between two rows — up closes the top one, down closes the bottom, a piece is captured every turn.
Every fir tree has a square the shuttle moves between. Take it one move earlier and the opponent's whole structure is dead.
Don't lay out both rows in a row — the opponent counts the threat. Disguise one unfinished row as a block and complete the second half with your last move.
While the shuttle has moved away, the return square is free for exactly one move. That is the only window to step in and jam the running mill.
Once the supply runs out, the value of a piece changes. What matters is not where it stands but how many free adjacent points it has — its mobility. A piece on a four-way intersection with two or three exits is worth twice a corner piece pinned between the opponent's. Count your army's total mobility: whoever has more "breathing" pieces dictates the tempo.
Hence the second victory condition — lock the opponent in. If they have no move, they lose even with a full army. So blocking in the moving phase is a weapon, not a defence: take away free points, drive their pieces into the corners. And as soon as a side is down to exactly three pieces, flying begins — its pieces jump to any empty point and sharply strengthen the weaker player. Hence the rule: while capturing pieces, don't bring the opponent down to three until you are ready to finish — ideally keep them at four, where there is no flying yet and mobility is minimal.
The blue piece in the centre is boxed in by red on every side: no moves — the side loses even with an equal number of pieces.
Before your move, gauge who has more "breathing" pieces. A mobility advantage almost always turns into a mill advantage.
Four pieces is not flying yet, but almost paralysis. Don't rush to take the fourth until you are ready to press straight down to two.
In its own flight a piece strikes across the whole board. Fly to the return squares of the opponent's running mill and to close your own rows — that is how lost games get pulled out.
Most losses come not from the opponent's brilliant play but from typical blunders. Learn to spot them and you will stop handing over pieces for free.
The opponent calmly blocks a single unfinished row. Until you threaten two mills at once, your set-ups are worth almost nothing.
You formed a row that has nowhere useful to move — three pieces frozen as dead weight. A mill is valuable for the ability to usefully open and close it.
The opponent quietly lays out a fir tree while you go about your own business. One missed move and the running mill is up and running — recovering is now nearly impossible.
You should take the piece that ruins a threat or breaks the opponent's running-mill set-up, not the one in plain sight. Often it is a lone piece on the pivot point.
A point closed in time (✕): two blues in a row with the third free — blocking the opponent's threat is worth more than your own combination.
Before you move a piece, look for two of the opponent's in a row with a free third. A missed threat costs more than any combination of yours.
Chasing an extra piece at the cost of position wrecks your own structure. Sometimes it is stronger not to capture a piece but to close the opponent's running mill.