(;
GM[1]
SZ[19]
AW[cc][dd][fd][kc][nc][pb][jp][dp][fp][ok]
AB[qc][pd][pf][qk][pm][pq][lp][cn][ci][cf][bd]
LB[pi:B][ok:1][pm:2][qj:A]
C[Problem 165. White to play.  

After the exchange of White 1 for Black 2, White's first instinct may be to attach at A. There is an interesting move here. Where should White play ?  

<See Reference Diagram 165 for Black 2 at B.> ]
;W[qq]
TR[pm]

TE[2]
C[Correct Answer.  

It seems as if Black has strongly reinforced the lower right by playing the marked stone. however, White can still attach at 1. The timing of this move is important; it must be played after Black has played the marked stone. ]
;B[qp]
C[In response to Black 2, ... ]
;W[pp]
C[... White cuts at 3. ]
(;B[qo]
LB[pr:A][oq:B][rq:C]
C[Black might extend to 4, but then White can live in the corner by playing A - Black B - White C. The way White plays is a strategic decision that depends on how the situation on the outside develops. ]
;W[oi]
C[In the meantime, White simply jumps to 2, threatening the right side. It is decisions such as these that make Go so interesting. <= ]
)
(;B[pr]
C[Variation.  

Black 4 is a fighting move. ]
;W[pn]
C[White attaches at 5, ... ]
;B[po];W[qn];B[on];W[qm];B[pl];W[qo];B[op];W[rp]
LB[pr:1]
TR[qq]
C[... and the moves to 13 are one variation. The result is not so good for Black. Still, Black 1 is a solid move. Therefore, White's timing in playing the marked stone is important.  <= ]
)
)