Attack or Defend First

When several squares look useful, play the move that changes the result of the game, not the move that looks busy. Use the same order every turn: your own win first, then your opponent’s win, then a threat.

Practice this opens the position on the play page with you as Black against the computer. The computer answers after your move. Diagrams are drawn for this page; row numbers and column letters match the 15 by 15 board. If you still have an unfinished online match in this browser, the site keeps that match instead of loading the lesson.

The position

It is Black’s turn. Black has G9, H9, I9, and J9. F9 is White, so K9 would be exactly five. White has G7, H7, J7, and K7, with I7 empty. I7 would be exactly five for White. There is also an empty quiet square, H11, which does not finish either line.

What each move does

1. K9. Black makes exactly five on row 9. The game ends before White can play I7.
2. I7. White’s gap is filled, so White does not win. Black also does not win. The game continues, and the win that was available on K9 is gone for this turn.
3. H11. Nothing is finished. White plays I7, makes exactly five on row 7, and White wins.

Attack first here because K9 is an immediate win. Defense is the right idea only when you do not already have a win.

Practice this position

The other way around

Change the position so Black does not have a five. Black’s row on 9 is only G9, H9, and I9. White’s broken four on row 7 is unchanged. J9 extends Black’s row to four, which is not a win. I7 is the only square that stops White.

What happens next: J9 does not make five. White plays I7 and wins. I7 does not win for Black either, but it is the only move that keeps the game going. Defend first when the opponent’s threat is a win and yours is not.

Practice the defense