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I just learned how to play GO today, and I was stuck on one thing in particular. This was the board state:

enter image description here

As you can see on the south-west corner (close to A1), I tried to capture my opponent's (which is a computer, 25 kyu) group of pieces. But I found out that I couldn't place my pieces on those empty squares because that would be a suicidal move. How do I acquire those pieces?

I was black and the computer/AI was white.

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    Who is white and who's black? Which corner is "south west"? perhaps the corner nearest the point A-1? If yes, say so. That's why the points are labeled. – Forget I was ever here Aug 9 '20 at 4:05
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    "How do I acquire those pieces?" Do you imagine that it should always be possible to capture pieces that are on the board? If so, why should the game ever end? – Karl Knechtel Aug 9 '20 at 12:41
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    @Karl Knechtel This is the first game I have ever played. People don't know anything when they're born. They rely on instincts and other people for help. Same way, I used my instincts and I thought I could capture that group of pieces on the board. Because that didn't work, I asked other people for help. If that's a problem, please don't hesitate to tell me. Thanks! – Sriswaroop Koundinya Aug 9 '20 at 13:17
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    @ForgetIwaseverhere: I see no need to discourage the questioner from using compass points, which seem to me self-evident, given the convention that N is up, and capable of useful nuances such as SSW (or even “NE by E”, though I realise that 32nds are not well known!). – PJTraill Aug 10 '20 at 9:55
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    As you now know from the answer you accepted, you were mistaken in thinking it was possible; I think @KarlKnechtel was simply trying to help you ask yourself the right questions, but his comments unfortunately came across as rather discouraging. I hope you take to the game, which can provide a lot of satisfaction whatever level you reach, and enjoy it. If you want to find out more about it, Sensei’s Library, at senseis.xmp.net , is one of many useful sources. – PJTraill Aug 10 '20 at 10:07
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In order to capture a group, you need to deprive it of all "liberties," the empty spaces touching the stones. In this case, the southwest group has two liberties, on A1 and C2.

However, as the rules don't allow you to leave any of your own stones without liberties at the end of your turn, you can't play on A1 due to suicide, and the same goes for C2. In order to capture that group, you'd have to somehow play on A1 and C2 at the exact same time, but you only get to play one stone per turn.

So how do you capture the southwest group? The answer is, you can't! Welcome to an important fundamental part of Go strategy: "Life and Death."

The southwest group is in a state where it is invincible, and nothing you do can capture it, so we refer to this group as "alive." On the other hand, a group which can't save itself from being captured is "dead."

How does a group become alive? In the exact way shown on your board here. Inside the group are two separate liberties (empty spaces), and since you can't play inside both spaces at the same time, capturing the group is impossible. Liberties inside a group are called "eyes," and if a group is capable of making two eyes, it is alive.

A group that can't save itself is a group that has no way of making two eyes. These groups are considered dead. Typically Go players do not even go through the process of capturing groups that are clearly dead, and instead just capture the dead stones once the game is over.

Though, playing out the position to check if the stones are really dead does not affect the final score, as each additional stone added to the dead group is worth a point for the capturing player, but each additional stone played to complete the capture fills up one point's worth of the capturing player's territory, so it all balances out in the end.

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  • Great answer! So the key is to surround the pieces before the group gets too huge? – Sriswaroop Koundinya Aug 9 '20 at 13:18
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    If you really have to capture, then yes surround before it's too huge, though to clarify it's a specific kind of huge which has space for eyes in the middle. (See the ladder technique here for an example where you can let their group get quite big in a controlled manner and still capture it.) However, the real key is that this is a game of tradeoffs: it's fine if their group gets huge and invincible as long as in exchange you're able to get an even bigger invincible group somewhere else! – Benjamin Cosman Aug 9 '20 at 15:21
  • What @BenjaminCosman says about trade-offs is very important, but perhaps even more important is to realise that you win by making more territory than your opponent; you only need to capture if they would otherwise have more than you. – PJTraill Aug 10 '20 at 10:13
  • @Sriswaroop Koundinya: Yes, that's the idea. More specifically, you have to prevent the group from forming two separate eyes. So it's not all about size; a group of as few as six stones can become alive in the corner, and as Benjamin said, even a large group can still be dead if it can't make two eyes. And as PJ said, not being able to capture a group is fine if you're already winning, one captured stone is worth no more than one controlled square of territory. In the case when you're ahead, your opponent is the one who needs to take the risk of trying to capture you. – David S. Aug 10 '20 at 14:32
  • @SriswaroopKoundinya Adding to what David S. said, my Go teacher preferred to say that you need to take away eye-space if you want to kill a group. Limiting the total size of a group is a way to take away eye-space. But you can also play stones into the area that your opponent wants to take, which are connected to stones outside. No eye can touch an opponent's stone, so such a connected chain of opponent stones is very effective at taking away eye space. You don't care how big your opponents group is if it's just meandering through a two-space corridor with your stones on both sides. – cmaster - reinstate monica Aug 15 '20 at 22:15

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