Defence · 6 min

How to Block Your Opponent and Turn Defence into Attack

Good defence is not about blocking every move. You only need to stop the biggest threat, then use that same blocking stone to launch a counterattack of your own.

Read the position before you block

Before every move, count how many stones your opponent has in a row and how many open ends remain. Three stones with two open ends are more dangerous than four stones with only one, because an open three can grow into an open four that you cannot stop. Look for the threat that could become five in a row on the very next turn and deal with that first. Panic blocking often spends a stone on a line that was never going to win.

Defensive priorities in order

Block a four: if your opponent has four in a row, you must take the open end immediately.
Block an open three: if there is no four, stop the three that has two open ends.
Create a counterattack: after blocking, look for a move that makes a three or four for you.
Keep your stones connected: do not block with a stone that is too far from your own shape.

Block the end, not the middle

Against a row of four stones, blocking in the middle does nothing, because your opponent can still complete the line at the remaining end. Put your stone on the open end instead. With three stones the situation is more subtle: blocking one end can be enough if the other end is already closed by another stone or by the edge of the board. Checking both ends before you choose is the difference between a real block and a wasted turn.

Turning the position around

After you block, look for a move that creates a four and forces your opponent to defend again. If you can make two threats at the same time, they can only answer one of them, and the other becomes your winning line. This is why the best defensive move is often also an attacking move: it stops the immediate danger while changing who has to react. A block that leaves you passive simply gives your opponent another turn to build.

Counterattack drills

Give your opponent an open three, then find the block that also creates a three for you.
Play the AI and try blocking with a counterattack instead of blocking and waiting.
Review a lost game: which blocking move gave up a chance to attack?