EVENT
BOARDSIZE 19
SETUP W C16 C15 D17 F17 D3 G3 R10 D8 
SETUP B D15 D14 C14 C5 F5 Q4 R16 P17 
MARK A@D10 C@C3 B@H4
COM
Problem 131. Black to play.  

Before pincering the white stone on the left side, does Black
need to make any preparatory moves ? Of course, Black would like
to finish up on the left side in sente so he can play on the
right side before White.  
ENDCOM
B 1 D10
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Black must first play 1.
ENDCOM
  VAR
  B 1 H4
  COM
  Failure.

  If Black plays 1 here, ...
  ENDCOM
  W 2 H3
  COM
  White will play 2 ...
  ENDCOM
  B 3 J4
  W 4 J3
  COM
  ... to 4, ...
  ENDCOM
  B 5 K4
  W 6 D11
  COM
  ... then extend to 6.
  <=
  ENDCOM
  ENDVAR
W 2 F8
COM
When White jumps to 2, ...
ENDCOM
B 3 H4
W 4 H3
  VAR
  W 4 G4
  MARK 3@H4
  COM
  White's failure.

  In response to Black 3, White must not cut through with 4 ...
  ENDCOM
  B 5 G5
  W 6 H5
  COM
  ... and 6.
  ENDCOM
  B 7 H3
  W 8 H2
  B 9 J2
  W 10 G2
  B 11 H6
  W 12 J5
  B 13 G7
  COM
  After Black 13, White will be find herself in a severe fight.
  (See Problem 151 in Get Strong at Joseki 1.)
  ENDCOM
  ENDVAR
B 5 J4
W 6 J3
B 7 K4
W 8 L3
B 9 E4
COM
... Black can force with the sequence to 9, ...
ENDCOM
W 10 E3
B 11 H8
COM
... then cap at 11.
<=
ENDCOM