Gomoku Strategy: Threats and Forks

Gomoku is won by forcing moves. Once you understand which shapes must be answered, the game becomes a race to create two threats at once.

Know the forcing shapes

Four: four stones in a line with one open end. Must be blocked immediately.
Open four: four in a line with both ends open. Can’t be stopped — it wins.
Open three: three in a line with both ends open. Must be answered now, or it becomes an open four.

Build a fork

The winning idea is a single stone that makes two threats at once — two fours, a four and an open three, or two open threes. Your opponent can only block one.

Prepare forks by placing stones where your lines cross, a few moves before you cash them in.

Chain fours to win by force

A four must be blocked, so a sequence of fours gives your opponent no choice at all. If you can see a chain of fours that ends in a double threat, you have a forced win — this is exactly what the Hard computer searches for.

Defend early

Block open threes as soon as they appear, ideally on the end that also helps your own lines. Waiting until an open three becomes a four leaves no choice about where to block.

Here, five or more in a row wins, so long lines of six count too.

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Gomoku Strategy: Threats and Forks

Know the forcing shapes

Build a fork

Chain fours to win by force

Defend early

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