Life and Death
The Go board is a battlefield. Opponents will try to surround and capture your stones — and you’ll try to do the same to theirs. Let’s learn how to make groups alive and how to kill enemy groups.
- Life and Death
- Suicide?
- Pointless sacrifice?
- Continuous sacrifices
- Life
- Life without two eyes?
- False eyes
- False eyes and kos
Suicide?
Let’s revisit the suicide rule. It’s illegal to place a stone where it would have no liberties — unless that move captures some opponent stones.
Capture White’s group
Playing A immediately is illegal. First you must reduce white’s liberties by playing B.
Pointless sacrifice?
This time White has two liberties on the inside. It’s still possible to capture this group by making what looks like a pointless sacrifice. The idea is to force White to answer, reducing their own liberties.
Continuous sacrifices
This time White has three liberties on the inside.
It’s still possible to capture this group by repeating the same process. Each time White is forced to capture Black’s sacrificed stones, White’s internal space gets smaller.
Life
It’s time to finally reveal Go’s magic defense mechanism:
Making Two Eyes.
In the last example, did you notice that Black’s first move was inside the group, instead of starting from the outside like before? Let’s see what happens if Black doesn’t do this.
White again has three liberties inside, but this time Black starts attacking from the outside.
Now White can divide those internal liberties into two separate areas — two eyes.
A group with two eyes is alive. No matter how Black plays, they can’t fill both eyes, so the group can never be captured.
Life without two eyes?
Below, Black has four internal liberties in a straight line. As your eye space grows, it becomes easier to split it into two eyes. In this position, we don’t even need to move yet:
- If White plays A, we respond at B
- If White plays B, we respond at A.
- This situation is called miai — there are two vital points and White cannot play both.
Since we have miai to live, we can tenuki and play the more useful move at T.
If White tries to kill, respond at the other vital point.
Key Point: You don’t have to actually form two eyes to be alive, as long as you have multiple options to do so when the opponent attacks.
False eyes
In the examples so far, the stones were all solidly connected. But when there are cutting points, the situation can change.
White’s eye at B isn’t solid. Black can play A to turn B into a false eye. Next Black can capture some of the stones forming the eye.
False eyes and kos
Sometimes a false eye will involve a ko. But if winning the ko-fight still doesn’t save the group, we consider the group dead right away.
Some kos don’t matter
Black must throw-in a stone at A. This stops White from playing there to solidify the eye at B.
A becomes a false eye, and White is dead even though there is a ko-fight left over.
Since the group is already dead after Black’s throw-in at A, in a real game both players will move on to unresolved parts of the board. Also in a tsumego (life and death) problem, it’s considered solved at that point. Remember from the shortcuts section that players don’t usually play out all the moves needed to capture dead stones. In this case, even though a ko fight is involved, the group will eventually die anyways.
Some kos matter
Here’s an example where the ko really matters.
Black plays A to try to make B a false eye.
But to keep the eye false, Black must win the ko-fight.
In a real game, both players would have to weigh whether to keep fighting this ko or play elsewhere and concede it. In a tsumego problem, though, it’s considered solved as soon as the ko-fight begins. The group’s fate now hinges on the ko: if there was no way to kill it cleanly without a ko, that already counts as a success for the attacker.