EVENT
BOARDSIZE 19
SETUP W C17 D16 F16 L17 O17 Q18 K4 D4 F4 
SETUP B R17 Q16 Q14 R9 Q3 M4 C6 B16 C14 C11 
MARK 1@M4
COM
Problem 163. White to play.  

Black has played 1, expanding the moyo he has made from the Chinese
Opening and defying White to invade. How should White attack
? 
ENDCOM
W 1 P9
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

Lightly capping with White 1 is the correct strategy. It flattens
Black's moyo ...
ENDCOM
  VAR
  W 1 Q5
  COM
  Failure.

  White 1 leaves something to be desired.
  ENDCOM
  B 2 R4
  COM
  After Black 2, White must worry about being attacked.
  ENDCOM
  W 3 P9
  COM
  If White now caps at 3, ...
  ENDCOM
    VAR
    W 3 Q7
    COM
    If White jumps to 3 here, ...
    ENDCOM
    B 4 P9
    COM
    ... Black jumps to 4, making a moyo at the top and leaving the
    two white stones below under attack.
    <=
    ENDCOM
    ENDVAR
  B 4 P8
  COM
  ... Black attaches at 4.
  ENDCOM
  W 5 O8
  B 6 Q8
  W 7 O9
  B 8 O7
  W 9 N7
  B 10 N6
  MARK 1@Q5
  COM
  After the sequence to Black 10, White 1 has become a wasted move.
  <=
  ENDCOM
  ENDVAR
  VAR
  W 1 B4
  COM
  Failure.

  Locally, White 1 is an excellent move, but one of the strategic
  principles of Go is 'never let your opponent perfect his moyo.'
  ENDCOM
  B 2 P9
  COM
  This is exactly what Black does when he jumps to 2. Black's moyo
  is now very large and solid and Black has taken a commanding
  lead.
  <=
  ENDCOM
  ENDVAR
B 2 Q7
COM
... since he must answer at 2. There is still aji left in the
corner.
<=
ENDCOM