EVENT
BOARDSIZE 19
SETUP W D16 D4 F3 H3 K16 L17 O17 
SETUP B K4 H5 Q4 Q10 Q16 Q14 M15 K14 
COM
Problem 38. White to play.  

Black mapped out a vast moyo. White has to prevent Black from
solidifying it. Where should she play ? 
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W 1 O4
USER
CORRECT ANSWER
ENDUSER
COM
Correct Answer.

White should play the high approach move with 1.
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  VAR
  W 1 D10
  COM
  Failure.

  White 1 is too passive.
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  B 2 Q6
  COM
  Black strengthens his position with 2 and, because of the presence
  of the four marked stones, White will find it hard to reduce
  the scale of Black's moyo. Therefore, White must invade the bottom
  right before Black has a chance to reinforce his moyo with 2.
  <=
  ENDCOM
  ENDVAR
B 2 Q6
COM
Black 2 is the natural response, but ...
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  VAR
  B 2 M4
  MARK @@Q6 A@O6
  COM
  Variation.

  Black might pincer with 1. If White answers by jumping to A,
  Black will jump to @ and White's two stones will be in trouble,
  floundering in the middle of Black's moyo without a base.
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  W 3 Q5
  COM
  Therefore, White attaches with 3.
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  B 4 R5
  COM
  If Black 3, ...
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    VAR
    B 4 R4
    COM
    The ladder favours White.

    Black could respond to White's attachment by extending to 2 and
    White will not be able to make sabaki.
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    W 5 P5
    COM
    If White 5 here, ...
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      VAR
      W 5 R5
      COM
      Therefore, White plays 5 here and, ...
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      B 6 P5
      COM
      ... if Black 6, ...
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      W 7 P4
      COM
      ... White cuts with 7. Since the ladder is in White's favour,
      she can fight in this position.
      <=
      ENDCOM
      ENDVAR
    B 6 S6
    COM
    ... Black 6 puts White on the spot.
    <=
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    ENDVAR
  W 5 R4
  COM
  ... White crosscuts with 4 to make sabaki.
  <=
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  ENDVAR
W 3 M4
COM
... now White 3 threatens to link up with its allies on the left,
so ...
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B 4 J3
COM
... Black must play 4 ...
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W 5 H4
B 6 J4
COM
... and 6.
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W 7 M6
COM
White can now come out into the center in good style with 7 ...
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B 8 K6
W 9 M8
COM
... and 9.
<=
ENDCOM