“If you don’t like ko, don’t play go” is one of the first proverbs a beginning go player is likely to hear. Like a lot of go proverbs, its meaning isn’t necessarily clear when you first hear it. “Play forcing moves before living,” for example, makes no sense when you’re a beginner with no idea what either term means. Ko is a little different. In its most basic form it’s one of the fundamental rules, but its strategic implications remain obscure for a long while.

Dia. 1: A basic ko

This is the most basic ko position. If it’s White’s turn, she can capture at the marked point. Black cannot recapture due to the rule of ko, which states that you cannot immediately repeat the previous board position. This is the aspect of ko that you learn when you first begin playing. The importance of the rule takes much longer to learn.

Dia. 2: 4-4 point enclosure

This is a small knight’s move enclosure from a 4-4 point. This is one of the first enclosures beginners play, because the 4-4 point is relatively “easy.” Unfortunately, it shows an inconsistent strategy in the play of most low- and mid-level kyu players. The 4-4 point is aimed at the outside. It strikes a balance between the top and left, and it is expected to have long-range implications. It is not territorial. The knight’s move enclosure, though it has a long history in professional play, has a different purpose than most beginners understand. They think that playing this move protects the corner and guarantees fifteen points.

The problem with this strategy is the 3-3 point, which is marked in the diagram.

Dia. 3: The classic invasion

After a 3-3 point invasion, it’s impossible for Black to kill the invasion cleanly without ko. This is one of the easiest and clearest ko positions. White needs to capture 6 at ‘A;’ if Black backs down from the ko and plays at ‘A’ himself, white can often live unconditionally in the corner and has other options for forcing a ko.

One mistake I’ve found myself making in situations like this is considering the ko in isolation, so that I never make the attempt to form a ko as in Diagram 3. Rather than being a misunderstanding of ko itself, I think this stems primarily from a misunderstanding of ko threats—the other important part of ko strategy.

Dia. 4: Kong Jie 7-dan vs. Hu Yaoyu 8-dan

This position is from a game between two Chinese professional players. Kong Jie 7-dan is Black, while Hu Yaoyu 8-dan is White. White is attempting to reduce Black’s territory on the bottom side. The seven stones on the bottom side have very poor prospects by themselves, so White plays the marked stone at the 2-3 point. If Black responds submissively, white can merely connect and his group will live. This would amount, roughly, to a 40-point reduction in Black’s territory. Impermissible!

Dia. 5: Finding the ko

With moves 1–7, Black initiates a ko. First he cuts; White connects. Black plays 3. If Black played 5 first, White would simply play at 3 and he would be guaranteed an eye in the corner, which is enough to live. White 4 ensures that if he gets the chance he can play at ‘B’ in order to live. Black 5 puts White in atari, White 6 accepts the challenge to a ko, and Black’s capture at 7 begins the ko. Since Black captures first, White must find the first threat.

, , , , and take ko.
Dia. 6: The fight

White’s first threat, at 1, threatens to connect three dead white stones with the center group, and in so doing cut off twelve black stones. Black responds at 2, so White takes the ko. Black threatens white locally at 4. Local threats are usually a very good option if possible, so Black has the upper hand in this fight. I’m not sure that it’s quite one-sided enough to be a “flower-viewing ko,” but it’s certainly good for Black. White responds at 5, and Black takes the ko. White’s 7 and 13 threaten the integrity of the lower left; Black’s 10 and 16 are two more local threats. At 23, it seems that white can’t find any threats large enough; he ignores Black’s threat and ends the ko. He has lived in the corner, but at a huge cost—the entire marked central group has died, cut off after Black follows through on his threat with 24.

This is devastating to White’s chances. White resigns after a desultory effort in the upper right. (If you’re curious, you can view the game at Go4Go.net.)

It’s unclear to me why White plays the ko, to be honest. Although Black seems ahead prior to White’s attempted reduction, it seems odd that Hu Yaoyu would miscount the number of threats. Is it possible that he overlooked the internal threats?

To be continued…