And at the top level, South Korea has supplanted Japan as the No. 1 go country. This is not because Japan has become weaker, but because South Korea has had an explosion of children wanting to learn go after the success of Lee Chang Ho, who became world champion at the age of 16. Women are also making great strides, and regularly beat top pros.
World Championship for Women
We'll start out with the solution to last week's problem from a game between Izumi Kobayashi, the Japanese female Honinbo playing Black, and Chinese player Rui Naiwei, who lives and competes in South Korea and won a title open to both men and women. This game was played in the first round of the World Championship for Women.
Solution 1: After black 1, many people would probably want to play at A to try to cut off the marked black stones. But before doing anything rash, let's try to accurately assess the position.
First, if we look at the marked black and white stones and ask ourselves whose stones are functioning better, it is clear the black stones are not making any territory, while the white stones below are making territory and the ones above are building influence.
Second, while recognizing that the connection between black 1 and the other black stones to the left is not secure, we should also be aware that it often does not pay to keep punching away if a knockout is not inevitable. It is important to keep a balance between attacking and defending, between building thickness and making territory.
Third, the weakness at A does not mean we have to play there--an attack at B might be more effective and still other moves might turn out to work better than A, depending on how the game progresses. In other words, White should keep her options open and focus on another part of the board. If there are no weak groups on the board, usually the best move is where the space is widest--around white 2. White is clearly leading at this point.
Diagram 1: Feeling the heat, Kobayashi then starts a sharp battle by attaching at 1. White has little choice but to keep pushing with 2 through 8, then jump out with 10--but black 11 is a strong move. After white 12, the moves through 20 are forced. However, White's next move was a blunder. Where should White have played?
Diagram 2: After black 1 (black 21 in Diagram 1), White should have played at 3, and then at 2. This would have given White an easy win. In the game, however, White played at 2 immediately, allowing Black to play at 3, a good move that set up a squeeze with 5 through 11. White is clearly in trouble at this stage. With 12 and 14, White tries to make eye shape, but black 15 is an aggressive move that destroys any possibility of this happening. Note that the comments in Solution 1 apply to white 14: White is aiming at exploit weaknesses in Black's connections. The moves through 24 prepare for the cut at 26 while making eye shape. Now, Black is in trouble. Instead of 15, Black should have played at 16, letting White off the hook. That would have left Black with overwhelming thickness on all sides and a chance to attack White's stones in the lower right quadrant.
Diagram 3: White 14 and 20 are played in ko where the marked white stone is. Black 17 and 25 are played in ko where the marked black stone is.
The moves from 8 start a tumultuous battle where the objective is to cut and avoid being cut. Ignoring the threat of white 12, the combination of 11 and 13 starts a ko. The rest of this diagram depicts the flow of ko, ko threat and counter-ko threat.
Diagram 4: White 4 is played in ko where the marked white stone is, while white 20 connects where black 1 is. During the ko, White starts another cutting action with 2. Black 3, and 9 through 17, are an excellent escape combination, but in the end, Black had to give in to White's relentless fighting spirit. Rui Naiwei won the game by resignation. As you can see, the style of the women is not different from the men.
Solution to last week's Problem 2
The question was how Black should respond to white 4.
There is not really an all-purpose solution to such general moves. There are at least four reasonable moves to consider. Let's have a look at all of them, and their strengths and drawbacks.
Solution 2A: Black 1 is not a stylish move, but it creates deficiencies (cuts) in White's shape. After forcing 2 for 3, White has to play at 4 to protect against the cuts. The moves through 9 follow. The advantage is that the marked black stones are efficiently placed. The drawback is that White can later cut with A, followed by black B, and white C. Usually Black will have to play at D next, forcing white E, which makes a lot of corner points.
Solution 2B: Black 1 is a steady move that stops White from starting a wild fight. Even if White pushes with 2 and cuts with 4, Black simply answers with 5. The drawback is that it does not do very much except to prevent White from living in the corner.
Solution 2C: Black 1 is a severe move. After white 2 and 4, Black has two cutting points. Since it would be a bit of an overplay to connect at A, it is probably best to connect the other cutting point with 5. White 6 is slightly more effective than the same move in Solution 2B, because a cut at B is a threat. White could precipitate the threat by approaching around C. Note that White can still cut at A to make eyes quickly.
Solution 2D: Defending the corner, black 1 is a stylish move. However, white 2 is a good answer. Black can now play as in the previous diagram or he can simply connect at 3. The moves 4 through 6 are a possible follow-up, for White to make eyes easily. It is a simple response, but it lets White off the hook too easily.