Defending in gomoku is not only about where to put a stone. It is also about when. Every stone you place on defence is a move you did not spend on your own lines, and gomoku is a race: the first player to build a threat the other cannot answer wins. Block too early and you fall behind in that race. Block too late and there is nothing left to block.
This article gives you a way to judge timing. It will not replace experience, but it will stop the two most common mistakes: panicking at every pair of enemy stones, and relaxing one move too long.
The currency of gomoku is tempo
Think of each turn as one unit of time. A move that forces your opponent to answer, such as making a four or an open three, "costs" them a turn: they must spend their stone on your threat instead of their own plan. A quiet move that forces nothing gives them a free turn.
A defensive stone is quiet by nature. So every time you block, ask: is this threat serious enough to be worth a whole turn? If the answer is no, the stone is better spent building.
The ladder of danger
Enemy shapes can be ranked by how many free moves they need before they become unstoppable:
- Four (open or closed): zero. It threatens five next move. Block now.
- Open three: one. Next move it becomes an open four, which wins. Block now, unless you have a four of your own to play.
- Two threes that share a point, or a three and a two crossing: often one. The shared point is where a double threat would appear. Consider occupying it now.
- Closed three: two. It needs a stone to become a closed four, then you block the last end. It can usually wait.
- Open two: two or more. It is a seed, not a threat.
The ladder tells you what to do in most positions. The skill is noticing the third rung, the crossings, because they do not look dangerous until one stone turns them into a double threat.
Why blocking early can lose
Imagine the opponent has three scattered pairs on the board. If you block each pair as it appears, you spend three turns on defence and your own stones end up scattered too. Meanwhile the opponent spent those turns placing stones that each touch two or three of their lines. Soon one of those stones creates two threats at once and you cannot answer both.
The early blocks were not wrong individually; each closed something. But collectively they surrendered the initiative. The lesson: a block that only blocks is a small loss of tempo. A few of them in a row become a big one.
Why blocking late loses faster
The opposite mistake is more dramatic. You see an open three, decide your own attack is more important, and play elsewhere. The opponent extends to an open four. Now there are two winning points and you can block only one.
The only time you may ignore an open three is when your own move is a four, which forces the opponent to answer first. After they block your four, you are back to facing the open three and must block it then. If your move is only a three, it does not force anything: the opponent makes the open four and wins before your three matters.
The crossing-point test
Here is a quick test that catches most double threats before they happen. After every enemy move, look at the new stone and draw the four lines through it: horizontal, vertical and both diagonals. On each line, count enemy stones within four points. If two lines each have two or more enemy stones and they meet at an empty point near the new stone, that empty point is a candidate for a three-three or four-three next move.
If you find such a point, occupying it is usually better than blocking any single line, because it breaks two lines at once. It is the defensive version of a double threat.
Blocked ends versus freestyle timing
Under the Vietnamese blocked ends rule, a line of five only wins if at least one end is open. That makes early blocks slightly more valuable: once you have closed one end, you only need to close the other end later, and even a long line becomes harmless. In freestyle, a five wins regardless of the ends, so the closed four remains a real threat and you cannot count on "half-dead" lines.
In practice this means that under blocked ends you can sometimes block a closed three a move earlier than usual, knowing it will cost the attacker more to revive it. Under freestyle, stick closely to the ladder above.
Timing when you are ahead
When your own attack is strong, the question becomes: can I make a threat instead of blocking? If you can play a four, do it; the opponent must answer and you keep the initiative. If you can make an open three that the opponent must block, and their current threat is only a closed three, you can often afford it.
Chaining forcing moves like this, four after four, three after three, is how most gomoku games are won. The defender who blocks every quiet shape never gets the chance to start such a chain.
Timing when you are behind
When the opponent has the initiative, your goal is to survive until they run out of forcing moves, then strike back. Answer every four and open three accurately, and on each block, prefer the point that also builds your line. Sooner or later the attacker plays a quiet move, and that is your turn to become the attacker.
Practise the judgement
On the home page you can play the computer at four levels. A useful drill: before every move, say out loud which rung of the ladder the opponent's biggest threat is on. Then decide whether to block or build. After the game, look back at the moves where you lost the initiative. The defense section covers specific shapes in more detail, including how to block well.
Frequently asked questions
Is it ever right to ignore an open three?
Only when you can play a four first. A four forces an answer; a three does not.
Should I block a closed three?
Usually not yet. It needs two more moves to become unstoppable, so a building move is often better, unless the block also builds your own line.
What is a crossing point?
An empty point where two enemy lines meet. One enemy stone there could create two threats at once, so it is often worth occupying first.
Does the blocked ends rule change timing?
A little. Lines closed at one end are weaker under that rule, so an early block can be worth more than in freestyle.
How do I get the initiative back?
Survive the forcing moves accurately, choose blocks that also build your lines, and strike when the attacker plays a quiet move.
