EVENT
BOARDSIZE 19
SETUP W C3 D3 E3 D2 E2 F2 G1 H2 G3 H4 J4 S3 R4 Q5 R6 S5 T4 R9 R10 P11 B18 C18
SETUP W D18 E17 E16 D16 C16 B15 C13 M15 N14 N16 O16 O17 P18 Q18 Q17 R17 S18 T18 
SETUP B D1 C2 B3 C4 D4 E4 F4 G4 F3 H5 R3 Q3 Q4 O3 Q10 Q11 R11 R12 B16 B17 C17
SETUP B D17 E18 F19 G18 F17 C10 J17 L16 M16 N17 N18 O18 P17 P16 Q16 R16 S17 T16 S15 
COM
Another important attacking principle: 

###################################
The ultimate purpose of an
attack is to threaten your opponent's stones in such a way that
you gain profit, either by securing territory or by building
influence.  
################################### 

In other words, don't try to kill stones you are attacking. Chase
them, harass them, tease them, torment them; but don't make any
great effort to kill them. If it turns out that you are able
to kill them, all the better, but don't make that your ultimate
goal. This Diagram is an example (Black to play)..  

ENDCOM
B 1 M13
COM
Black has strong positions at the top and on the right, which
he uses to attack the four white stones at the top with 1.
ENDCOM
W 2 L15
COM
White runs away with 2, ...
ENDCOM
B 3 K13
W 4 K15
COM
... 4 and ...
ENDCOM
B 5 C15
W 6 A17
B 7 H13
W 8 H15
MARK 3@K13 7@H13
COM
... 8, hoping to link up with her secure position in the upper
left corner, while Black presses with 3 and 7. Note that the
value of each of White's moves is zero. In contrast, Black is
building influence that radiates throughout the board. Clearly,
Black's moves must be good.
ENDCOM
B 9 F16
MARK 5@C15
COM
Black 5 and 9 exploit the aji of his four dead stones in the
corner, and ...
ENDCOM
W 10 F15
B 11 F13
COM
... Black 11 forces White ...
ENDCOM
  VAR
  B 11 E15
  COM
  Some players might be tempted to try and kill the white stones
  with the atari of 11, ...
  ENDCOM
  W 12 A16
  B 13 E14
  COM
  ... followed by 13 in this variation.
  ENDCOM
  W 14 F13
  COM
  But White would then threaten the black stones on the left with
  14 ...
  ENDCOM
  B 15 E13
  W 16 G13
  COM
  ... and 16, ...
  ENDCOM
  B 17 E11
  W 18 H12
  MARK 13@E14 11@E15 17@E11
  COM
  ... then make shape with 18 after Black defends with 17. The
  black stones in the center are now thin and it is White who has
  taken the initiative in the center. Black 11 and 13 are completely
  unreasonable.

  [Continued as "Problem 4"] 
  ENDCOM
  ENDVAR
W 12 E14
COM
... to defend at 12.
ENDCOM
B 13 D12
COM
Finally, Black plays 13 and his influence dominates the center
and works beautifully with his wall below. This is a textbook
example of an attack.

[Continued as "Problem 4"] 
ENDCOM