EVENT
BOARDSIZE 19
SETUP W C17 C16 D15 D13 C12 F17 H17 G15 H15 J15 K15 K16 N16 P16 P17 Q17 R16 S16 S17 H13 J12 
SETUP B C18 D17 E18 E16 E15 E14 G14 F12 D4 Q4 J16 J17 K17 L16 L15 M15 M14 L13 K14 R18 R17 Q15 Q16 R15 
COM
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Attack from a position of
strength.  
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If the stones that are used in your attack are weak, they could
end up being the ones attacked. Consider the Diagram (Black to
play).  
ENDCOM
B 1 J10
COM
Black caps with 1 and it seems as if he is building influence
in the center ...  
ENDCOM
W 2 K11
COM
... while forcing White run away with 2 ...  
ENDCOM
B 3 L9
W 4 M11
COM
... and 4.  
ENDCOM
B 5 N9
COM
Black keeps up the pressure with 5, but ...  
ENDCOM
W 6 M17
COM
... suddenly White plays a forcing move with 6 ...  
ENDCOM
B 7 L17
W 8 O14
MARK 5@N9 3@L9 \t@R15 \t@Q15 \t@Q16
COM
... and jumps to 8, splitting the marked stones from their allies
on the left. Black now has two weak groups and it is hard to
tell who is the attacker and who is the one being attacked. Both
sides are in for a hard fight and the outcome is far from clear
(Taken from Problems 50 and 135.). If Black already had a stone
at 8, Black 3 and 5 would be a devastating attack and White would
be crushed.  

[Continued as "Problem 3"] 
ENDCOM