Gomoku

Gomoku (五目並べ, “Five in a Row” in Japanese) is the ancient n-in-a-row strategy game played on a 15×15 or 19×19 grid. Two players take turns placing stones (black and white, like Go); the first to get 5 in a row (horizontally, vertically, or diagonally) wins. Gomoku is mathematically deeper than Tic-Tac-Toe but lighter than Chess — and the game was proven (1993) to be a forced first-player win on the standard 15×15 board with “free” rules.

How to play

• 15×15 (sometimes 19×19) grid of intersections, like Go.
• Two players: Black moves first.
• Take turns placing one stone per turn on an empty intersection.
• Stones don’t move once placed.
• First player to get 5 stones in a row (horizontal, vertical, or diagonal) wins.
• Game ends in draw if board fills without a 5-in-a-row.

The math: solved for Black

In 1993, Allis et al. proved that “free” Gomoku (no opening restrictions) is a first-player win — Black, with perfect play, can always force a win. To balance the game, professional tournaments use “renju” rules with restrictions on Black’s opening moves, which approximately equalize the chances.

Beginner strategy

• Centre control. Like Chess and Go, the centre of the board is most valuable. Open near the centre.
• Block immediate threats. Once opponent has 4 in a row, you MUST block. 4 unblocked = imminent loss.
• Create double threats. A “fork” — two simultaneous 4-in-a-row threats — is unblockable. Set these up.
• Don’t ignore diagonals. Diagonal 5-in-a-rows count too. Watch all 8 directions.
• Use stone density. Connected stone groups have multiple winning lines. Build dense clusters.

Intermediate strategy

• The “open four” (双四). Four stones in a row with BOTH ends open — opponent can only block one end. This is a guaranteed 5-in-a-row.
• The “open three” (双三). Three stones with both ends open. If unblocked, becomes an open four next turn.
• The “single three” + threat. A three with one end blocked + another open-three or open-four = winning combination.
• Block before attacking. Opponent’s open three is dangerous; block first, attack second.
• Pattern recognition. Expert Gomoku is dominated by recognizing 5-10 key threat patterns.

Advanced strategy

• VCF (Victory by Continuous Fours). A chain of “open four” threats that force opponent to block, while you build the next threat. Gomoku’s primary winning technique.
• VCT (Victory by Continuous Threats). Like VCF but with mixed threes and fours. More flexible.
• Stone shape evaluation. Expert players evaluate stone arrangements (X-shapes, L-shapes) for their winning potential.
• The 4-3-3 pattern. Open four + two open threes = unblockable.
• Endgame planning. Late-game stones become less flexible. Set up your winning configuration early.

Renju (the balanced variant)

Renju is the professional tournament variant of Gomoku, designed to balance the game by handicapping Black:

• Forbidden moves for Black: Black cannot create “double-three” (two open threes simultaneously), “double-four” (two open fours), or “overline” (6+ in a row).
• White has no restrictions.
• These rules effectively neutralize Black’s first-move advantage, making Renju approximately balanced.
• Professional Renju leagues exist worldwide, particularly in Japan, China, and Russia.

Gomoku history

• Ancient origins. Gomoku-like games appear in China and Japan over 2,000 years ago.
• Edo Japan: Gomoku is a popular Japanese household game.
• 1899 — Renju formalized: Japanese Renju rules published. Black’s restrictions added.
• 1937 — first international Renju competition.
• 1993 — Allis proves Black wins: Free Gomoku is solved. Demonstrates need for Renju balancing.
• 2000s — international Renju league. Russia, Japan, China dominate professional Renju.

Why Gomoku is loved

• Simple rules. 5-in-a-row, no captures, no special pieces.
• Tactical depth. Threat creation and blocking require real planning.
• Visual clarity. The board state is easy to read at a glance.
• Scalable. 5-min casual games to 1-hour tournament battles.
• Cultural importance. Strong tradition in East Asia.

Common mistakes

• Missing open threes. Open threes become open fours next turn. Block them immediately.
• Building single-direction threats. Multi-direction threats are unblockable.
• Ignoring diagonals. Diagonals count as 5-in-a-row.
• Trading without strategy. Stones don’t move; trades aren’t an option. Every placement matters permanently.

Variants

• Free Gomoku. 5-in-a-row, no opening restrictions. First player wins with perfect play.
• Renju. Tournament version with Black’s restrictions.
• Pente. American Gomoku variant with capturing.
• Connect-N. Other in-a-row variants: Connect Four (4), 5-in-a-row (Gomoku), 6-in-a-row.
• Caro (Vietnamese variant). 5-in-a-row but only “exactly 5” wins; 6+ doesn’t.

FAQ

• Q: Can I make 6 in a row? A: In free Gomoku, 5+ wins. In Renju, “overline” (6+) by Black is forbidden — it loses for Black.
• Q: What’s an open three? A: Three of your stones in a row with both ends unblocked.
• Q: Why do tournament games use Renju? A: Free Gomoku is solved for Black. Renju restrictions balance the game.
• Q: How is Gomoku different from Tic-Tac-Toe? A: Larger board, longer line (5 instead of 3), and stones can come from any direction. Much deeper.

For other n-in-a-row games, try Tic-Tac-Toe, Connect Four, Ultimate Tic-Tac-Toe, or Hex.