Invasion tactics

Timing is important when mounting an invasion. When an invasion destroys the territory of one's opponent, a player must make sure that his opponent does not, seemingly out of the blue, create another viable territory. Particular care must be taken about the 3-3 point.

Diagram 1: The sequence to 13 is the most basic invasion strategy at the 3-3 point when there is a stone on the 4-4 star point (black 1). White has gained about 10 points in territory, which is nothing to sneeze at, but the influence Black builds can be worth a lot more than that. Note that the hanging connection of 13 is essential to finish Black's wall. If he fails to make this move, White won't hesitate to cut at A. In addition, black 13 forestalls a cut at B. If Black already had a stone at one of the points indicated by the X's, then this joseki would be an ideal choice for White as the black stones would be overconcentrated-i.e. his stones are not working together for maximum effect.

Diagram 2: As the result in the previous diagram is not particularly favorable for Black, he can try the double hane of 5 and 7. White is virtually forced to capture with 8 and 10, but now Black can capture the corner and gain a lot of profit. White gaining territory in the corner. Although not absolutely necessary, white 14 is a thick move that is often played soon in the game. In principle, the result is good for White if there is a black stone around the X's (as white 14 then splits the black position). But White would be overconcentrated if there is a white stone around the X's. Note that there would be some aji (bad potential) in the corner if White exchanges A for B. After this exchange, moves at E and F become a threat, aiming at white C, which Black cannot answer with a move at D.

Diagram 3: If Black already has played the marked stones, instead of capturing the corner with 11 and 13 in the previous diagram (allowing White to take the vital point with 14), Black should play there himself with 1. If White answers with 2, Black can capture the corner. Even if White tries to split Black's stones now with 6 and 8, black 9 to 13 form an excellent combination that makes use of all Black's stones.

Reference 1: If White persists and tries to capture the marked black stone, Black has a great sequence to 31 in which he sets up a ladder to capture the three white stones 14, 24 and 28. This is all thanks to the moves 1 to 3 in Diagram 3.

Diagram 4: White will capture with 2 giving Black a chance to give atari with 3. White will usually play at the spot where the marked black stone was before, which is then followed by a black move at A. Once more, this gives Black terrific thickness.

Diagram 5: If White does not like this, he has a tricky alternative. After Black 7 in diagram 2 (black 1 here), White can try to confuse the issue with the combination of 2 and 4, aiming at the double-atari at A. To defend against this threat Black can play at A himself or at B. As B usually leads to an inferior position, A is the better move.

Diagram 6: This is a game played between Masaki Takemiya (white) and Koichi Kobayashi (black) for the Judan title in 1992. After black 23, White invades with 24. Black now has the choice to block at A or at B. A may seems to be better, but if White gets sente (such as in the variation in Diagram 1), he can play at C, which greatly reduces the effect of the wall Black has just created.

Diagram 7: Aiming for a result similar to that in Diagram 4, Black plays the double hane of 3 and 5. Countering, White plays the combination of 6 and 8 and Black plays at 9. White 10 and 12 grab the outside but Black profits with 11 and 13, while the exchange 4 for 5 is a heavy loss for White. Trying to make use of his dead stones in the corner, White plays at 14, pulls back with 16 to create damezumari (shortage of liberties), and then goes on to cut with 18 and 20 to play out his ace with 22, forcing Black to add a stone in the corner. In the ensuing fight White manages to live on the right side with 24 and 32 as well as extend into the center, destroying most of Black's influence in the process.

Solutions to last week's problems

Solution 1: If the marked white stones are strong (e.g. White has stones around the triangles), he can invade at the 3-3 point. Last week, we saw how small the territory Black would be able to retain if he descended at 3. Therefore, if there are no prospects for an attack on the white center group, the correct response is black 2. After white 3, Black can play at 5 or 4. Playing at 4 usually is the better choice. Note black 6-White could extend to 8, but if Black then connects at 7, he makes miai (play one or the other) of capturing white 3 or the three stones in the corner. White has no choice but to comply and capture with 7 after which black 8 completes the combination to get the best result territorially.

Solution 2: White sometimes plays the combination of 1, 3 and 5. Usually this is not worthwhile as it forces Black to play a good move at 6 and then play a hane on top of two stones, severely limiting White's room. With the moves to 21, White takes gote (plays the last move of a sequence, allowing the opponent to play elsewhere), but he makes about 10 points of territory and he aims at moves at A, B, C, D or E later. Black has no reason to be dissatisfied as his wall is thick, radiating strength all over the board. White should only choose this way of playing if he wants to settle his stones quickly and the influence that Black builds does not play a large role.