Gomoku looks like a game about building lines. It is really a game about forcing moves. If you can name the threat on the board, you almost always know what to play.
The threat ladder
| Pattern | Description | Must be answered? |
|---|---|---|
| Open two | Two in a row, both ends free | No |
| Open three | Three in a row, both ends free | Yes, almost always |
| Simple four | Four in a row, one end blocked | Yes, immediately |
| Open four | Four in a row, both ends free | Cannot be answered — it wins |
| Broken three | Three with a gap, e.g. XX.X, ends free | Yes |
The ladder explains the whole game. An open three becomes an open four next move; an open four has two winning points and cannot be blocked. So the moment an open three appears, it must be dealt with.
How to block an open three
There are three options and they are not equal. You can block either end, or play in a way that creates a stronger threat of your own so the opponent must respond instead.
Blocking the end that also extends one of your own lines is best. Blocking the end that gives the opponent a second direction to develop is worst. When both ends look similar, block the one nearer the centre — it has more room behind it.
Broken threes
The pattern XX.X — three stones with a gap — is as dangerous as a solid three, because filling the gap produces a four. Beginners consistently miss these, because the eye looks for solid lines.
The block for a broken three is usually the gap itself, since that point does double duty: it stops the four and sits on the opponent's line.
Fours are forcing but not winning
A simple four demands an immediate block, which means you keep the initiative — but you have also used up that line. Playing fours for the sake of it burns your own threats without gaining anything.
The exception is a forcing sequence: a series of fours that each force a block, manoeuvring the opponent's stones into positions that help you, ending with a double threat. That is the standard winning method at higher levels.
Don't spend your fours early
Each four you play is a threat you can never use again. Save them until you can see how the sequence ends.
Double threats: the actual win condition
Because any single threat can be blocked, winning requires two at once. The common combinations are four-and-three, three-and-three, and four-and-four. A four-and-three is the most reliable because the four must be answered first, and then the three becomes a four with the opponent out of time.
Building toward one means placing stones that belong to two potential lines simultaneously — which is why the centre of the board, where more lines cross, is where games are decided.
Reading order
- Do I have a five? Play it.
- Do they have a four? Block it.
- Do I have a four that leads somewhere? Consider it.
- Do they have an open three? Block it.
- Can I make a double threat? Play it.
- Otherwise, extend the line with the most future potential.
Running this list in order prevents almost every gomoku loss. Most defeats come from step two or four being skipped.