You are probably familiar with the story ...

By Rob Van Zeijst

You are probably familiar with the story of the Trojan horse, in which Greek soldiers hid so they could sneak into the enemy's territory. A similar technique is used in the endgame of go. This technique is called placement tesuji or oki, which is a clever move placed inside the opponent's group.

Placement tesuji

In the endgame, accurate reading of the board is important, but a few techniques will help improve your endgame. This week, we will look at oki-tesuji, which can help earn extra points, and also prevent the formation of eyes.

Diagram 1: The white position has a weakness Black can exploit.

Diagram 2: Black 1 is a good nozoki, a move in which a stone "peeps" between two of the opponent's stones. This move forces White to connect with 2. Black 3 then puts White on the spot as the marked white stone now lacks sufficient liberties (damezumari). If White plays at A, black will answer with B, and vice versa.

Diagram 3: In this situation, Black is able to reduce White's territory.

Diagram 4: Black 1 forces White to connect at 2. Black then links up his stone with 3 and 5, while White is busy defending his eye-space with 4 and 6. Black can now seal off the center with A or play elsewhere. Note that White could play at A instead of 6, but that would leave his corner open to attack.

Diagram 5: If White fails to mount a proper defense and plays the marked stone, Black can reinforce at a later stage, with the marked stones. Then, he can kill White's stones with the combination 1 through 7. If White captures two stones with A, Black plays at 1 again to take away a possible White eye here.

Solutions to last week's

problems

Solution 1A: If it is White's turn, he should exchange 1 for 2 and 3 for 4 as soon as possible. Black must answer or else his corner dies.

Solution 1B: The clamp at 1, last week's theme, works very well here. White will probably need to compromise with 2 and 4, giving Black the opportunity to cut into his territory even further in sente with 5 and 7.

Solution 1C: (White 16 connects where 9 was captured) Resisting with 2 will probably lead to the sequence to 17 with a large territorial loss for White. Note that Black can force A for B.

Solution 2: White can capture one stone in sente with 1 and 3. Black must answer with 2 and 4, otherwise he dies. Therefore, if it is Black's turn, he cannot leave his stone hanging. He should connect at 1, which is answered by white A. In other words, this is sente for both parties.

Solution 3: White should clamp at 1. Black has to submit with 2, allowing White to connect in sente at 3. Black must play at 4.

Solution 4A: White's clamp at 1 is a real pain for Black. Connecting at 2 allows White to connect with 3 and threaten Black's base with 5. Black is in serious danger, although this depends on how strong White is on the outside.

Solution 4B: In response to white 1, if Black plays at 2. White's strongest attack is 3 and 5 if he has enough ko threats. Black has no choice but to eventually cave in with 6 and 8. This gives White a strong shape and extra points, while Black's corner is small, even if he can still connect at A or B.

Solution 5A: Black 1 is a good clamp. White has to play at 2 and 4 but Black still will scoop out most of White's territory.

Solution 5B: If White resists with 2, he loses his marked stones in the sequence through 9.

Problems

Problem 1: White to play first. What is his best move?

Problem 2: This is from a recent game between top pros. White exchanged 1 and 3 for 2 and 4, then played elsewhere. Black, however, followed with a decisive oki-tesuji move. Where did he play?

Want to find out more? Come to Ben's Cafe in Takadanobaba, Tokyo (03-3202-2445), where the English speaking go community congregates every Sunday. You can enjoy free lessons, 11 a.m.-1 p.m. Ben's Cafe can be accessed at www.benscafe.com.

Van Zeijst is a four-time European go champion and European representative at the Fujitsu World Championship.