Some of the most beautiful wins in gomoku look almost magical: the attacker makes four after four after four, the defender is forced to block every time, and at the end two threats appear at once and the game is over. This technique has a name among serious players — victory by continuous fours, often shortened to VCF.
It is also one of the most practical skills you can learn, because it lets you win with certainty from positions that look only slightly better.
The idea
A four leaves the defender exactly one move: block the winning point. That means a sequence of fours is completely forced. If every move you make is a four, the defender never gets a free move, and you control exactly where their marks go.
A VCF is such a chain of fours, ending with a move that creates two winning points at once — typically a double four (two fours with one move) or a four that also makes an open four. At that point the defender cannot block both, and you win.
Why it works
Ordinary attacks give the defender choices. When you make an open three, the defender can block either end or make a four of their own. When you make a double three, the defender can interrupt with fours. But when every move is a four, the defender has no choices at all, and no time to make threats of their own.
The only thing that can break a VCF is if one of the defender's forced blocks accidentally creates a five-threat for them — a four of their own. That is why, while calculating a chain, you must check each forced reply: does it give them a four?
The finishing move: the double four
The most common end of a VCF is a double four. One move creates two separate fours, each with its own winning point.
In the diagram both of X's fours are blocked at one end, yet the combination wins, because the two fours have different winning points. Under blocked-ends rules it also wins: each resulting five has an open end (j8 or h10).
Finding a chain
Finding a VCF is a matter of looking for fours you can make and asking where each one leads. A practical method:
- List your possible fours. Every line with three marks and a way to five gives you at least one four.
- For each four, note the forced reply. Where must the defender play?
- Look at your new mark. Does it add to another of your lines? After the defender's forced reply, can you make another four?
- Repeat until you find a move that makes two fours or a four plus an open four.
You do not need to see the whole chain at once. Often you see two or three fours ahead, and the last step reveals itself as you get closer. But do not start a chain you cannot finish: every four you make spends a line, and a failed VCF leaves you with nothing.
A chain in words
Imagine X has a closed three on a row, and a column two that crosses the row just beyond the three's open end.
- X extends the row three into a closed four. The new mark is exactly the crossing point, so the column now has three marks. O must block the row's winning point.
- X now makes a four on the column. O must block its winning point.
- X's column four-mark sits next to another X shape on a diagonal, which now becomes a four as well… and so on.
Each step, X's new mark does two jobs: it makes the current four, and it prepares the next line. Each step, O's mark goes where X decided. When the chain ends in a double four, the game ends.
VCF versus ordinary attack
Not every winning position contains a VCF. Often the attacker must use open threes along the way (sometimes called a VCT, victory by continuous threats), which gives the defender more options. But when a VCF exists, it is the safest win, because no calculation of the defender's alternatives is needed.
In practical games, a good habit is: whenever you have two or more lines of three, spend a few seconds looking for a chain of fours. You will not always find one. When you do, it wins.
Defending against continuous fours
Once a VCF has started, the defender can only follow — so the defence must come before. Signs that a VCF may be coming:
- The attacker has several threes, especially closed threes, close together.
- Those threes point toward each other or cross near empty points.
In such positions, a quiet defensive move that occupies a key crossing or blocks the end of one three can break the chain before it starts. It may look passive, but it removes the attacker's most dangerous resource.
Continuous fours under blocked ends
Under Vietnamese caro rules, remember that a four blocked at one end, if the defender also blocks its winning point, is dead forever. In a VCF this does not matter — you are not trying to reuse those lines — but it matters if the chain fails. A failed VCF in blocked-ends play leaves a trail of permanently dead lines. Be sure before you start.
Why VCF matters even when you do not play it
Knowing how continuous fours work changes how you evaluate positions. A player who understands VCF looks at a board with several of their own closed threes and thinks "these are ammunition", not "these are dead lines". Closed threes that seem harmless are exactly the lines that provide the fours for a chain. So, paradoxically, a VCF-aware player keeps more closed threes on the board and spends them later, all at once, in a forced sequence.
Practice
Against the computer on the home board, look for positions with several of your threes and try to find a chain of fours before making any move. Even if you do not find one, the search trains exactly the calculation skill you need. When you do win with a chain, replay it from your account and write the moves down; you will begin to recognise the shapes that make chains possible.
Frequently asked questions
What does VCF mean in gomoku?
Victory by continuous fours: a winning sequence in which every attacking move is a four, so the defender's replies are all forced.
How does a VCF usually end?
With a double four, or a four that also creates an open four — two winning points the defender cannot both block.
Can the defender escape a VCF?
Only if one of their forced blocks creates a four of their own. Otherwise, a correct VCF wins.
Is continuous fours the same as a four-three?
No, but they are related. A four-three is a single move; a VCF is a chain of fours that often includes or ends in a four-three or double four.
