(;
AB[ed][ee][ef][eg][pd][pq][oq][nq][no][lo][mo][oo][pl][ep][do][co][bp][cq][dm][ro][rn][rm][qn][rl][pj][qj][ln]
AW[fb][dc][dd][de][df][ph][qi][bm][cn][bo][an][cp][qr][qq][pp][po][on][nn][mn][mp][pn][pm][qm][ql][nl][ll][qo]
TR[rl]
LB[rk:A][rj:B]
PL[W]
C[White's response to the marked play?

Keeping Black's right side group unsettled will allow White to gain elsewhere while attacking.  Both A and B work, but is one better than the other?

Source:
    Go World #15, pp. 6-7
    Hashimoto Shoji 9P vs. Kato Masao 9P]
(;
W[rj]
C[This move looks natural, but leads to a serious problem.];
B[rk];W[ri];B[qk]
(;
W[rp]
C[The problem is that White has to block here to keep Black from living immediately on the right side.

Now Black can play the all-important first move in the fight on the outside.]
)
    (;
    B[rp]
    C[For example, if Black plays here, ...];
    W[qp];B[rq];W[rr];B[sq]
    C[... Black lives.  Now White can no longer attack an unsettled group to gain profit elsewhere.]
    )
)
    (;
    W[rk]
    C[The best move (from the game).  The reason will be clear soon.];
    B[rj];W[qk];B[sk]
    (;
    B[rp]
    TR[rk]
    C[Note that because of the marked play, Black's peep here can no longer make eye-space to live on the right side.];
    W[qp];B[rq];W[rr]
    C[Black only has one eye on the lower right edge.]
    )
        (;
        W[pe]
        C[A very severe leaning attack from the game.]
        (;
        B[od]
        C[Black would like to defend here, but ...];
        W[oi]
        TR[pe]
        C[... with the marked stone's indirect support, White can come back here to attack the right side group.];
        B[rh];W[ri];B[si];W[qg];B[rg];W[qf]
        C[White's stones are working perfectly together.  Black's group still does not have a second eye, and so is in considerable danger.]
        )
            (;
            B[rp]
            C[The actual game continues.];
            W[qp];B[mk];W[nj];B[rh];W[qe]
            C[The fighting is very complicated, but Black's unsettled group is a burden.  White went on to win this game.]
            )
        )
    )
)

