I’m learning so I’m going through all beginner problems I’m finding and I do not get this:

The problem starts like this; I am trying to protect the black stone on the right side.

After I played, the board looks like this:

enter image description here

But the problem doesn’t get completed unless I play that last move:

enter image description here

And I don’t understand: what does this move bring?

  • I have no idea why black should play the last move at this spot and not at the spot one below to the left. That would also reduce white to 1 liberty (which is mandatory), and is far simpler.
    – mafu
    May 1, 2020 at 17:20

1 Answer 1


The black group in the upper corner has two liberties, as does the main white group before you play that last piece. Therefore, if you had instead decided to play elsewhere on the board, white could have decided to capture the black group and done so before you could save it.

With that final spot filled in, you are now guaranteed to capture the white group before the black group is captured. That means you are free to play elsewhere on the board without being in danger of losing this corner - if white ever plays here you can always safely respond.

Superficially, it may look like that last piece is easily captured, but every move that white could make has a response that puts them back at one liberty away from capture, so it's not as vulnerable as it appears.

  • Ok, I get it; I also realized that if white tries to extend in the bottom I can still stay one step ahead. I really don’t see these patterns yet! Thanks.
    – Thomas
    Apr 28, 2020 at 12:46
  • 2
    Btw, the correct move is not the one shown, but rather extending the two black stones down to the right edge, taking the other liberty of the white stones. Because, the way the situation is shown, white still has the possibility to play that move themselves, or take the black stones, to regain a liberty. This can be used as a ko threat for around 40 points. If black played the extension, there is not ko threat, whatsoever. If you can capture with a no-nonsense move, do it. May 19, 2020 at 7:12

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