There are a variety of martial arts and other fighting sports where it is important to keep your distance and strike at the right time. Examples are karate, kendo, taekwondo, and boxing. In judo it is less obvious because it has two stages. In the first stage, both judoka are standing up and trying to maneuver themselves into a favorable position to make a decisive throw or at least get the opponent off balance. When you get too close before the throw you are likely to lose balance yourself, so for an attack to be effective you have to keep a solid stance. This is a moot point because when you move in the direction of your opponent, he can use your inertia to make a throw or sacrifice. On the other hand, once the adversaries are on the ground, it is important to use your weight and strength to keep the other person down by keeping direct physical contact.
In go we also have these same elements. You try to keep a distance and wait for the right timing to attack. Sometimes you make sacrifices when your opponent attacks, and sometimes you try to put your opponent on the wrong foot to obscure your real motives. However, when you get down to direct fights where the stones touch each other, it becomes a different thing. There are many situations where the brute force of taking away liberties is important. These situations are referred to as  semeai or capturing races. Let’s now get our hands dirty and find out the basics of capturing races.
Problem 1
Problem 1: Black to play
Both the Black and the White marked stones have four liberties. Where should Black play to capture White’s stones?
Show Solution
Solution 1
Solution 1
This is a straightforward semeai. The first player to fill in a liberty of the opponent wins. After Black 5 it is clear White’s four stones cannot be saved. If White plays at A, Black will capture with B. In general, the rule is to start filling liberties from the outside. Black would normally start at 1, not at B. Often this would lead to the same result, but there are plenty of exceptions. There is another good reason to make this a habit. In case there is a ko, the moves 2, 4, and A can be used by White as ko threats. The value of each of these ko threats is approximately 18 points. However, if you start with B instead of 1, the value would become 20 points (because White would threaten to capture the White stone at B in addition to the initial four stones).
For full details on ko, please refer to the book [All About Ko by Rob van Zeijst and Richard Bozulich, published by Kiseido].
Problem 2
Problem 2
Black plays first. How should he play to capture eight White stones? There are two things you can do. First, you can to visualize each move and visualize the final result. Second, you can count the number of liberties for each group and reach a conclusion about the final result. Remember, start filling liberties from the outside.
Show Solution
Solution 2
Solution 2
Black should start filling in liberties from the outside, for example at 1. If White fills in a liberty, too, Black should continue to do so. As you can see, after Black 13, White’s stones have just one liberty left—at B—while Black has two—at A and B. If White plays at A, Black naturally captures with B. Visualizing all these moves is a major task and you can easily make a mistake. When there are many liberties, as in this case, it is better to count the number of liberties of both groups. White has seven liberties plus a shared one at B. Black has seven liberties plus a shared one at B as well. If Black goes first, he will win the race by one move. This is the same with longer and more complicated semeai.
Reference 1
Reference 1: Black to play
Black should not fill in the shared liberty, i.e. 1. This results in White losing a liberty, but in the process Black loses a liberty, too. If White and Black keep filling in liberties, Black loses the capturing race. After White 12, Black has one liberty, against two for White. If Black plays at A, White captures with B.
Problem 3
Problem 3: Black to play
The moves through 14 are part of an old joseki. Black needs to capture White 10 and 12. How does he do it?
Show Solution
Solution 3, part 1
Solution 3, part 1
Black should keep White’s liberties down to three or two at all times. Black 15 through 19 are the tesuji to this end. Black then ataris at 21. What follows after 22 is a standard tesuji combination.
Show Solution
Solution 3, part 2
Solution 3, part 2
Exchanging 23 for 24 before connecting at 25 is a clever move. This way Black wins the semeai in case White plays at 27 instead of 26. Black now ataris at 27 and White cannot connect. Therefore White will usually play at A; Black captures three stones by playing at 23, and White recaptures one stone with B.
We have talked about two techniques so far. A third one is the ladder. Here is an example.
Diagram 1
Diagram 1
This is a variation of a joseki. However, White should not follow this variation if the ladder is bad for him because Black gets overwhelming influence. Incidentally, White 6 is caught in a ladder and cannot escape.
Diagram 2
Diagram 2
If White tries to pull his lone stone out, Black keeps it in atari at every step of the way. This is called a ladder and in the end, White is driven all the way to the edge. After Black 46, White has no way out and perishes.
Example from a pro game
In pro games, you can often find situations that involve multiple techniques for capturing stones. The following game, played in the Kisei League in 2006 by Kobayashi Satoru, 9-dan, who was Black, and Kato Atsushi, 8-dan, comprised the three elements we have discussed for capturing: net, filling in liberties, and a ladder.
Problem 4
Problem 4: White to play and avoid being trapped
Warning: This is a complicated problem even for top amateurs.
In the moves up to 55, Black grabs hold of the left part of the center, but leaves his stones in the lower right out in the cold. White 56 is a severe attack and Black tries to escape with 57 and 59. However, White offers fierce resistance with 60 and 62. Black’s problems really started long before this, and since he is a top pro, Black was well aware of this. So before the problem started he had already made an outline of his plans. His plan involves a combination of the net, filling in liberties, and a ladder as tactical ploys to invoke a strategic sacrifice.
Reference 4A
Reference 4A: Shortage of liberties
White cannot start a semeai right away with 1 and 3. Black 4 and 6 kill White’s stones. Capturing one stone with A does not work for White, as Black ataris with B.
Show Solution
Solution 4, part 1:
Solution 4, part 1: Black’s failure
In the game, White played 1 and 3. Black 4 is not possible because White will simply play 5 through 9 and capture the two marked Black stones.
Reference 4B
Reference 4B: White is tricked
After White 3, Black played a clever move at 4. If White just answers with 5, Black will play 6 and 8, but deviate after White 9. Black now has an absolute sente move at 10, i.e. White must answer at 11. Next Black 12 delivers a death sentence for White’s marked stones. They are short of liberties.
Show Solution
Solution 4, part 2:
Solution 4, part 2: Black sacrifices the corner
After Black 4, White therefore captures one stone, Black plays atari and White connects with 7. Next, Black answers 3 by extending to 8. White 9 and 11 were a clever interjection, which kept White ahead in the capturing race by playing 13 in sente before finally capturing the entire lower right corner with 15. For reference the next few moves are given. As you can see, Black sacrificed his stones in the lower right to build a huge center moyo.
Unfortunately for Black, White was able to reduce the top side of Black’s moyo enough to win the game.
Reference 4C
Reference 4C: Black is caught in a ladder
Instead of cutting at 4 as in the actual game (i.e. move 9 in the previous diagram), White could have kept pushing with 1 and 3. If Black tries to lock him up with 4 through 8, White can set up a ladder with 9 through 17 to capture three Black stones.
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By: zaphod stumbleko (Registered) on 22-04-2008 07:47