EVENT
BOARDSIZE 19
SETUP W D16 F16 R4 P3 R7 Q18 O17 L17 P13 P12 Q12 
SETUP B C14 D10 D4 R9 P9 P11 O12 Q16 Q14 R17 
MARK \t@Q12 \t@P12 \t@P13
COM
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  Leaning Attacks
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Another attacking technique is the 'leaning attack', that is,
attacking stones in one part of the board in order to build strength
for capturing or threatening stones somewhere else. Here is an
example.

The three marked stones in the Diagram are under siege, but Black's
stones are not strong enough to trap them. Therefore, ...
ENDCOM
B 1 O16
COM
... he switches to the top and attaches with 1.
ENDCOM
W 2 N16
COM
If White defends with 2, ...
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  VAR
  W 2 O13
  MARK \t@Q12 \t@P12 \t@P13
  COM
  Of course, White might decide to extract her marked stones by
  turning at 2 ...
  ENDCOM
  B 3 N17
  W 4 M13
  COM
  ... and jumping to 4.
  ENDCOM
  B 5 N16
  MARK 3@N17
  COM
  In that case, Black will play 3 and 5, taking the territory at
  the top right. Black is satisfied with this result (Taken from
  Problem 49.).

  [Continued as "Problem 6"] 
  ENDCOM
  ENDVAR
B 3 N15
COM
... Black hanes with 3.
ENDCOM
W 4 M16
COM
After White defends with 4, ...
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B 5 O13
MARK \t@Q12 \t@P12 \t@P13
COM
... Black comes back to finish off the marked stones with 5.
They can no longer escape and they don't have enough room on
the right to live.
<=
ENDCOM