Last week, we introduced the concept of lines of division between moyos, or potential territories. Without any preparation, we dived into a game that had just been played by two top pros.
Drawing the line
Go has many types of openings. Some players like small, but solid territories. Others like to map out huge territories, while still others start to fight right away. However, in many games territories exist with some kind of border between them. In such cases, redrawing the border in your favor becomes important.
Diagram 1: Two black and white shimaris (corner enclosures) sit opposite one another. If you were Black and it was your move, where would you play?
Diagram 2: Black 1 is right in the middle of the two shimaris. If White defends his stake with 2, and we assume both Black and White defend their turf with 3 and 4, we get the position shown here. The triangles roughly represent the borders of Black's territory, while the X's outline White's. Although each player used the same number of stones (four), the difference in their territory is clear. Black has divided the territories to his advantage.
Diagram 3: What happens if Black extends a little farther--for example at 1, or A, B, or even all the way to C?
Diagram 4: It would be nice if White defended his territory, but instead he invades with 2. Black moves at 3 to make a base, but so does White with 4. After having played four moves each, their positions are congruent. Compare with Diagram 2 to see the difference.
Diagram 5: Extending even farther--to black 1, for example--makes it easier for White to invade and more difficult for Black to make a base and settle in. Neither A nor B is an optimal extension from black 1.
Diagram 6: What about extending to black 1? White will happily extend to 2. If we next assume the moves black 3 and white 4 will be made--both good moves to defend their turf--it is easy to see Black gained no advantage from his first move.
Diagram 7: This position looks very different, but similar elements are present. White has a strong position in the lower-right part of the board, while he also has an extension in the upper-right corner. He can also cut at A, followed by black B, white C, black D and white E to build more thickness in the center. Black also has a moyo on the upper edge. In fact, all marked black and white stones form two competing moyos. Where is the dividing line between them?
Diagram 8: Black's best move is 1. White will probably jump to 2 and black 3 is a good follow-up move. If your answer was at A, that is good, too. However, White will play at 2, making a good shape. Black C is a good follow-up, but it is not as good as 1 and 3 shown here where you can clearly see White's moyo expanding and Black's shrinking.
Solution to last week's problem
Solution 2A: Black should cut with 1 and descend to 3. If White plays 4 to capture the two black stones, White is in for a surprise.
Solution 2B: Black 7 before atari at 9 is a strong move. This squeezes White and takes away his eye and liberties, too.
Solution 2C: If White forcefully connects at 10, black 11 through 15 fill in White's liberties, while white 12 through 16 desperately try to connect. However, White's lack of liberties becomes apparent as Black plays 17, capturing 12 white stones.
Solution 2D: For advanced players, there is another solution. Instead of following the previous diagrams, after black 3, White should connect at 4 to prevent the squeeze. After black 5, white 6 and 8 cleverly set up a ko. After black 9, to start the ko, White takes black 7 by playing where 6 was captured.
Problem
Problem 1: Where is the dividing line between these competing moyos? If Black moves first, where should he play? What about White?
The solution to this problem will be carried next week.
Want to find out more? Come to Ben's Cafe in Takadanobaba (03-3202-2445 or www.benscafe.com), where the English-speaking go community congregates every Sunday starting at 11 a.m. You can enjoy free lessons until 1 p.m.
Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.