Gomoku strategy: threats, forcing moves and double threats

The shape of a Gomoku game

Gomoku is a race between two players building threats. Since there are no captures and no passing, the only currency is tempo: whoever forces the other to respond keeps the initiative, and whoever runs out of forcing moves first has to defend until they lose.

1. Fours force. Any four must be answered.
2. Open threes force. An unanswered open three becomes an open four, which wins.
3. Double threats win. Every Gomoku victory is ultimately one move creating two threats.

Level 1 — Basic: stop losing in twelve moves

1. Block every open three, immediately

If your opponent has three in a row with both ends empty, you must block one end now. Next move it becomes an open four with two winning points, and no single move can stop it.

2. Answer every four

A four has exactly one winning point. Block it. There is no choice and no alternative worth considering.

3. Play near the action

A stone far from the fight does nothing. Until you are strong enough to know why you are playing elsewhere, keep your stones within two points of the existing cluster.

4. Build two lines at once

Prefer moves that extend two of your own potential lines. Stones that sit on the crossing point of two directions are worth roughly double.

5. Take the centre

The centre point has eight directions with maximum room. Edge stones are worth far less, because lines run out of board.

Level 2 — Intermediate: forcing sequences and VCF

Learn to count a forcing sequence

The core intermediate skill is VCF — victory by continuous fours. Because every four must be answered, a chain of fours lets you place stone after stone while your opponent is forced to block, until one of your fours also makes a five somewhere else. Before you start a sequence, count it to the end: a VCF that runs out leaves you worse off, because every four you made is now a dead shape.

VCT — victory by continuous threats — is the same idea including open threes. It is harder to calculate because open threes can be blocked at either end, which branches the search.

Build the double-threat shapes

The winning shapes have names, and they are worth recognising instantly:

Defend by counter-attacking

Pure defence loses Gomoku. If your opponent has the initiative, look for a block that also makes a three or a four of your own — forcing them to answer and handing the initiative back. Strong players choose which end of an open three to block on exactly this basis.

Watch the broken shapes

Three stones with a gap (●●·●) is a real open three, and it is the most commonly missed threat in the game. Scan for gaps, not just for runs.

Level 3 — Advanced: threat-space search, openings and Renju technique

Think in threat space, not in moves

Strong players do not search all moves — they search threats. The practical method:

1. List every move that makes a four or an open three.
2. For each, list your opponent's forced replies.
3. Repeat, and look for a position where two threats intersect.

Because forced replies are unique for fours, these sequences can be calculated to fifteen or twenty moves deep with practice — far deeper than a general search would allow.

Opening theory

Competitive Renju has a fully catalogued opening system: the 26 named three-stone openings (Chōsei, Kasumi, Ura-getsu and the rest), each analysed in detail, combined with Swap2-style balancing. Freestyle Gomoku has less formal theory but the same principle applies: Black's first three stones should form a compact shape with several directions available, and White must break the shape before it becomes a double threat.

Playing Renju as Black

The forbidden moves change everything. Black must build a winning attack without ever creating a double three or a double four, which means:

• Plan attacks that end in a four-three, which is legal, rather than a three-three, which is not.
• Watch for accidental forbidden moves in your own forcing sequences — losing on a technicality in a winning position is the classic Renju disaster.
• Remember that White can use your restrictions: White can build shapes where your only good reply would be a forbidden move.

Playing against an engine

A good Gomoku engine calculates VCF perfectly, so speculative attacks fail immediately. The only practical approach is to keep the position quiet, build stones that serve multiple directions, and avoid giving it any forcing sequence — then look for a double threat it did not have to defend against.

The mistakes that lose games

1. Missing a broken three — three stones with a gap.
2. Blocking the wrong end of an open three, when the other end also helps your own shape.
3. Starting a forcing sequence you have not counted. Every four you spend is a shape you can never use again.
4. Playing away from the fight to build something new — you will be forced back before it matures.
5. Pure defence. Blocking without threatening hands your opponent unlimited time.
6. Forbidden moves in Renju — losing a won position on a rule.

Common questions