In quiet positions gomoku is a game of shape and planning. But once threats appear — and they appear quickly — it becomes a game of order. Both players may have fours, threes and double-threat points at the same time, and the question is not "what is the best move?" in general, but "what must be dealt with first?" Get the order wrong once and the game is over.
This article gives a clear priority list and explains why each step comes where it does.
The priority list
When it is your move, go through this list from the top and stop at the first item that applies.
- You can make five. Make it. You win.
- The opponent has a four. Block its winning point. Nothing else matters.
- You can make an open four, or two fours at once. Make it. You win next move.
- You can make a four that also creates an open three (a four-three). Make it, as long as the opponent has no four of their own. It usually wins.
- The opponent has an open three. Either block it, or make a four of your own first and then block it.
- You can make a double open three. Make it, if the opponent has no open three or four to use first.
- Nothing urgent. Build: add useful twos, break the opponent's best shapes, prepare crossing points.
It looks long written down, but in practice most moves are decided at step 2, 5 or 7, and the check takes a second.
Why each step comes where it does
Steps 1 and 2: fives and fours
A five ends the game, so making one beats everything. A four threatens five on the next move, so if the opponent has one and you cannot make five yourself, you must block — any other move loses immediately.
Step 3: open fours and double fours
An open four and a double four both create two winning points at once. The opponent can block only one. Unless the opponent can make five first (which step 2 would already have caught), you win.
Step 4: the four-three
A four-three creates a four (which must be blocked) and an open three (which becomes an open four next move). The opponent is forced to block the four; then you turn the three into an open four. The only defence is if the opponent can generate fours of their own along the way to regain the initiative, which is why step 4 comes after checking the opponent's fours. See four-three combination.
Step 5: the opponent's open three
An open three becomes an open four in one move. You must stop it now — with one important exception. If you have a four available, you may make it first: the opponent must answer your four, and you still get to block their three afterwards. Sometimes that four even improves your position, because your four-mark may also block their three or build your own line.
In the diagram, j8 is the best of both worlds: it blocks O's three and creates a four for X at the same time.
Step 6: the double three
Two open threes created by one move usually win, because the opponent can block only one and the other becomes an open four. But a double three is slower than a four-three: the opponent is not forced to answer immediately with a specific move, and if they have a four available they can use it to interrupt. So check the opponent's forcing moves before relying on a double three. See double-three attack.
Step 7: building
When nothing is urgent, use your move to prepare. Quiet moves that add twos with potential and break the opponent's best shapes are what create future combinations. Read twos and potential.
The most common ordering mistakes
- Answering a three when the opponent has a four. It happens more often than you would think in fast games. Always check for fours first.
- Building your own three while the opponent has an open three. Your three is slower than theirs.
- Making a double three when the opponent has a four. They make their four, you must block, and your double three may be broken by their next move.
- Forgetting your own four as a defensive tool. When facing an open three, a four of your own can gain a tempo and sometimes block the three at the same time.
Priority under blocked ends
Under Vietnamese caro rules the list stays the same, but some items change value:
- A four that is already blocked at one end, if blocked again, becomes permanently dead. Making such a four spends the line for good.
- An open three whose ends already touch your marks at a distance may be less dangerous than it looks, because the eventual five might end up blocked at both ends. Count carefully before deciding it is harmless.
A worked decision
Imagine it is your move. The opponent's last mark made an open three on a diagonal. You have a closed three on a row, and one point on that row would make a four whose forced reply lands on a harmless empty point. There is also a quiet move that would give you a double three next turn.
Run the list. Step 1: no five. Step 2: no enemy four. Step 3: no open four for you. Step 4: does your four also make an open three? Suppose not. Step 5: the opponent has an open three — you must deal with it. You may make your four first, since it forces a reply and gains nothing for the opponent; then block the diagonal three. The quiet move for a double three (step 6) will have to wait. Played in this order, you keep the balance. Played in any other order — for example, the quiet move first — the opponent makes an open four and the game ends.
Practising the order
Against the computer on the home board, play a few games where you literally say the step number before each move: "step 2, block"; "step 7, build". It sounds slow, but within a few games the order becomes automatic. Then replay a lost game from your account and find the move where you applied the wrong step — it is almost always one of the four common mistakes above.
Frequently asked questions
What should I do first in gomoku when both players have threats?
Make five if you can; otherwise block the opponent's four; otherwise look for your own winning combinations; otherwise block their open three.
Can I ignore an open three?
Only to make a four of your own first. After the opponent answers your four, you must still deal with their three.
Is a double three as strong as a four-three?
Usually slightly weaker, because it does not force an immediate specific reply. The opponent may be able to interrupt with fours.
Does the priority list change in caro?
The order stays the same, but blocked ends change how much some threats are worth.
