Gomoku looks like a game of attack, but most games between beginners and intermediate players are decided by defensive errors. The winner rarely finds a brilliant combination; the loser leaves a door open. The good news is that the same few mistakes appear again and again, so fixing them improves your results quickly.
1. Looking only at the newest stone
After the opponent moves, it is natural to look at the stone they just placed and the line it extends. But the danger is often elsewhere: the new stone connects to older stones along a line you were not watching, or it prepares a crossing with a line from ten moves ago.
Fix: after every enemy move, scan all four directions from the new stone, and then glance at the lines through their two or three most recent stones as well.
2. Blocking the wrong end
When blocking a three, many players pick the end nearest to them or the end they noticed first. If the other end is where the attacker has more stones or crossing lines, the block barely slows them down.
Fix: block the end that is more useful to the attacker. If both are equal, choose the one that joins your own stones. See how to block in gomoku.
3. Blocking harmless shapes
Every stone spent on defence is a stone not spent on attack. Players who block every open two and every closed three soon find themselves with scattered stones and no threats, while the opponent's stones all work together.
Fix: use the ladder of danger: fours and open threes must be answered now; closed threes and twos can usually wait unless they cross. More in block early or late.
4. Missing the split three
A three with a gap (X, X, empty, X) is as dangerous as a solid three, but it is easier to miss because the stones do not touch. Players often block a solid three somewhere and leave a split three untouched until it becomes a four.
Fix: when you scan a line, count stones within any five consecutive points, not just adjacent stones. Three enemy stones inside five points with room at both ends is an open three, gap or no gap. See defending against an open three.
5. Ignoring diagonals
Horizontal and vertical lines are easy to see. Diagonals are not, especially on a large board and on a phone screen. A large share of surprise losses come from diagonal fours.
Fix: make diagonals a separate step in your scan. Tilt your head if you have to. Some players find it helps to trace the diagonal with a finger on the screen.
6. Playing a three against a three
When the opponent has an open three, some players respond with an open three of their own, hoping to race. It does not work: the opponent simply makes an open four and wins before your three matters.
Fix: remember that only a four outranks an open three. If you cannot make a four, block.
7. Giving up after a double threat appears
When a four-three lands, many players resign immediately. Sometimes that is right. But sometimes the three is not truly open, because of the board edge or a stone of yours two points away, or you have a chain of fours that breaks the attack.
Fix: before resigning, check two things: is the three really open, and do you have a four? It takes ten seconds and saves the occasional game. See surviving a four-three.
A note on the blocked ends rule
Under the Vietnamese blocked ends rule, a five that is closed at both ends does not win. Beginners sometimes forget that this applies to their opponent's lines too, and waste stones blocking lines that are already dead. If an enemy line is closed on one side by your stone and the other end would be closed by another of your stones, it cannot produce a winning five. (The board edge does not count as a block on this site, so a line running into the edge is still alive at its other end.) Leave it and build elsewhere. In freestyle this does not apply: any five wins.
Turning mistakes into practice
Choose one mistake from the list and focus on it for a week of games. For example, spend a week only on diagonals: after every enemy move, check both diagonals before anything else. Then move to the next mistake. Trying to fix all seven at once rarely works; fixing one at a time does.
Replaying your own lost games is the fastest way to see which mistakes you make most. If you sign in on the account page, games you play against the computer and online are saved, and you can step through them move by move afterwards.
A short self-check before every move
It helps to turn the list above into a routine you run before placing a stone:
- Is there an enemy four anywhere? Block it.
- Is there an enemy open three, solid or split? Block it, choosing the useful end.
- Is there a crossing point where one enemy stone would make two threats? Consider taking it.
- Have I checked both diagonals?
- If none of the above applies, what is my strongest move?
Running this list takes a few seconds once it becomes a habit, and it catches almost every mistake in this article.
Why these mistakes feel natural
None of the seven mistakes comes from carelessness alone. They come from how people look at a board. The eye goes to the newest stone, to straight lines and to shapes that touch. Gomoku punishes exactly those instincts, because the dangerous shapes are often older, diagonal and split. Knowing this helps: instead of blaming yourself after a loss, you can ask which instinct misled you, and train the opposite habit on purpose.
Frequently asked questions
What is the most common defensive mistake in gomoku?
Missing a threat because you only looked at the newest stone, or because it was on a diagonal.
Should I block every three?
Every open three, yes. Closed threes can usually wait unless the block also helps you.
Can I race an open three with my own three?
No. The opponent makes an open four and wins first. Only a four forces them to answer.
When should I resign in gomoku?
When there is a real double threat and you have no fours to play. Check both before giving up.
How do I stop missing diagonal lines?
Make them a separate step in your scan after every move, and replay lost games to see how often they cost you.
