New players learn quickly that you must block open threes. What takes longer is noticing that a player who does nothing but block will eventually face two threats at once and lose. Defence has to do two jobs.
Choose the block that builds
When a threat can be blocked at either end, the ends are rarely equal. Pick the one that lies on one of your own developing lines. A stone that stops their three and extends your two is worth two moves, and over a game that difference compounds into the initiative.
If neither end helps you, pick the one with less space behind it for the opponent — blocking toward the edge limits their future options more than blocking toward the centre.
Counter-threat instead of blocking
You are not obliged to answer a three if you can create a four. A four forces them to respond, and after they do, you can return to the original problem. This is how the initiative changes hands, and it is the main tool for getting out of a defensive spiral.
The risk is miscounting. If your four does not actually force, or if their three becomes a four while you are busy, the counter fails badly. Count carefully before choosing this over a simple block.
Two threats means you have already lost
If the opponent creates a four and an open three with one stone, no block saves you. Defence must happen a move earlier — when they have two separate twos pointing at the same area.
Seeing the double threat before it forms
The stone that creates a double threat has to sit where two of the opponent's lines cross. So look for the crossing points: places where they have stones in two different directions with a common empty intersection. Occupying that point pre-emptively defuses the whole plan.
This is the single biggest step up in gomoku strength. Reactive blocking answers threats; positional blocking prevents them.
Which threats to ignore
- A three with one end already blocked. It can only become a simple four, which you can block later.
- A two, unless it is the second two aiming at the same intersection.
- Any line that runs into the edge before reaching five — count the space before you spend a stone on it.
That last point catches people out constantly. Three stones near the edge with only one square of room can never make five, so blocking them is a wasted move.
Recovering the initiative
- Block in a way that extends one of your own lines.
- Look for a forcing four that gains a free move.
- Take the crossing point of their two developing directions.
- Once they have no immediate threat, build your own double threat rather than continuing to block.
Practising defence
Play as White against the club or strong setting. White is on the back foot by design in free-style gomoku, so every game is defensive practice. Use undo when you lose to a double threat and find the move, two or three turns earlier, where the crossing point was still available.