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Mutual Damage
Path: Endgame   · Prev: Semedori   · Next: Dame
Path: ForcingAndInitiative   · Prev: Tenuki   · Next: Fujite

    Keywords: EndGame

The general principle of mutual damage is to accept loss of territory, rather than defend territory, provided one can inflict equivalent damage on the opponent.

Defending is a way to accept gote. If you pursue a mutual damage plan, not answering the opponent's destructive plays directly, the possession of sente is actually in the balance for a while. You only find out who has it when the dust settles.

A mutual damage contest can be set off by miai: one player doesn't accept the idea that the other will get both of a pair of closely equivalent plays that are ordinarily sente. It can end in a game of 'chicken' (less colloquially, who blinks first).

Mutual damage in the opening is unusual.


[Diagram]
Mutual damage

Black 1 is a typical endgame hane, which threatens to heavily damage the opponent's territory if unanswered.

BillSpight: It is also what is normally called a double sente. It is worth around 9 points (miai), I believe, a huge play.


[Diagram]
No mutual damage

Locally, the sequence comes to an pause after 4 and Black has sente. He then uses his sente to execute another endgame hane.



Experienced players will agree the game is finished after White 8, and it is easy to see that Black wins by 3 points. It feels not entirely fair that Black has been able to play both hanes. Indeed, White has failed to apply the principle of mutual damage.

[Diagram]
Mutual damage

Mutual damage is in fact an application of the miai concept to the endgame. The moment Black plays 1 to damage White's territory, White MUST play the equivalent play at 2, if only out of self respect.

BillSpight: White 2 and answering Black 1 are worth about the same. However, as Dieter says, White cannot afford to let Black get both hanes. It looks like White should play White a - Black b before White 2. If Black has to play both points later, White a is aji keshi, but both sides will be invading, and this may be White's chance to inject some aji into Black's position. A difficult question.
See Costly Atari.


[Diagram]
Even

If Black answers White's hane, White keeps sente to defend against Black's hane at 6. The game ends after White 8 and White wins by 1 point.



[Diagram]
Mutual damage

One reason many players fail to apply mutual damage, is that the situation can become very confused if either player refuses to give in as in this diagram.

Another reason is that the situation never is as symmetric as in this simple example. Even here it isn't quite symmetric: White a is atari whereas Black b is not.

BillSpight: And White c threatens a snapback at d.



Still, if one player passively answers all "sente" endgame moves by the other, he or she follows a sure path to defeat.


TakeNGive (10k): Wow -- somehow I had never noticed this. Suddenly, BillSpight's endgame analyses take on new value.


Authors:



Path: Endgame   · Prev: Semedori   · Next: Dame
Path: ForcingAndInitiative   · Prev: Tenuki   · Next: Fujite

This is a copy of the living page "Mutual Damage" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.