Carpenter's Square - Wrong Attack

    Keywords: Life & Death, Question


How to answer 1?  

Recall that the status of the carpenter's square is a ko, when W1 is played at a.

W1 here is a wrong attack on the carpenter's square. Why?



The descent at B1 is the solution. It gurantees unconditional life (which includes seki, of course).

Solution (easy variation 1)  

If W2, then B3 onwards result in a seki.


If W2 here, then the placement at B3 is a tesuji.

If B3 at a, then White at B3, Black b, White c connects and kills Black at the same time.

Solution (easy variation 2)  

W4 connects, and B5 forms a seki.

Solution (main line)  

The main line starts with W4. B5 is the only move.

If B5 is played at a, then White 5, and Black dies (eyes win capturing races).

On the other hand, if W6 is played at a, then Black b is an atari in sente, forcing White c, and Black d makes two eyes.

Solution (main line)  

Hence, the main line continues with W6 capturing two Black stones. To avoid having White having an eye that wins the capturing race, B7 and B9 are vital. White can only connect underneath at W10.

Solution (main line)  

The finalle is the capture at B1, living because two White stones are also captured via connect and die.


The throw-in at B9 is a failure. W10 captures the B9 stone, and if Black a, then White b. Black's mistake is punished by shortage of liberties.


Carpenter's Square - Wrong Attack last edited by on January 20, 2014 - 15:04
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