Dochi Yose Tesuji

  Difficulty: Advanced   Keywords: EndGame, Tesuji

In a game played on November 24, 1705 between Honinbo Dochi (Black) and Yasui Senkaku (White), Dochi was losing by a few points in the endgame, when he suddenly played a brilliant yose (endgame) tesuji.


[Diagram]

Moves 225-232

Black 1 began the brilliant sequence of moves that saved the game for Dochi.

[Diagram]

Continuation (Moves 233-236)

The invasion made Black 1 and 3 sente, because if White does not capture the marked stone with White 4, Black would play at a and make a seki.

The invasion does not work if it is played after the hane-connect sequence.
-- Eric Suh?


You may wonder whether White has no other way to play. Let us have a look:

[Diagram]

If White plays 4 instead of a

The other reasonable move for White is to play 4 here instead of a. Black next plays 5 and 7. Is this sente, one may ask? If not, White has refuted Black's play.

[Diagram]

Black fails

Black 1 is an eye-stealing tesuji, as it makes the eye at a false, but White 2 is a good response and Black's attack runs into nothing. No matter how hard he tries, e.g. with Black 3 and so on, Black cannot get a seki, ko, or anything else.


The solution for Black is to play on White's vital point himself, with Black 1.

[Diagram]

Black forces a seki

White 2 is forced, as a move here would be rather awkward for White. Next, Black 3 is tesuji and Black 7 establishes an eye in the corner. Thus the position becomes a seki.


As can be seen, if White did not reply, he would lose his corner territory (in a seki with Black). Therefore, White had to add another move to defend his territory after Black played hane-connect at the top border. The hane became Black's sente and enables him to win the game.

--Arno


Question: What would happen if black were to play 233 as follows:

[Diagram]

Continuation (Moves 233+)

After playing at 1, Black could respond to a with b, connecting by taking advantage of white's lack of liberties, or else play at a himself to make an eye in the corner... --sj

If White seals at b, then White has enough liberties to kill Black in the corner since Black will be short on liberties due to an abundance of false eyes. Played this way it comes out pointwise identical to way the actual game. --Patrick


This is a copy of the living page "Dochi Yose Tesuji" at Sensei's Library.
(OC) 2009 the Authors, published under the OpenContent License V1.0.
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