(;CA[Windows-1252]FF[4]AB[pp][jn][po][np][in][pr][iq][pq][hr][ln][mn][nn][oo]AW[hp]
[op][qp][gq][oq][or][rr][on][pn][qn][jo][lo][mo][no][qo]PL[B]CR[oo][po][pp][pq]
[pr]C[Given that the marked chain has only three liberties, black must take a liberty of one of the two white chains, and must never let them both have 3 while white has sente. That means there are only a few interesting moves, and that many paths are rather straight and narrow. Still, the depth is huge, and there are many variations which fail only barely.

]
AP[GoWiki:2009]SZ[19]GM[1]GN[]DT[2011-08-13]PC[http\://lifein19x19.com/]MULTIGOGM[1]

(;B[nr];W[nq]
(;B[mq]
(;W[os]C[white must descend, otherwise black will connect under and squeeze]
(;B[ko]
(;W[lp]C[only way];B[lq];W[kp];B[mp];W[mr]C[only move, white has only two liberties]
;B[kq]
(;W[jp];B[jq]
(;W[ip]C[necessary];B[ms];W[ns];B[ls];W[lr];B[ks];W[kr];B[js];W[jr];B[is]C[The purpose of H2 is revealed])
(;W[ns];B[ip];W[kn];B[io]C[collapse]))
(;W[kn];B[km];W[io];B[jq]C[sente]
(;W[gr];B[ms];W[ns];B[ls];W[lr];B[ks];W[kr];B[js];W[jr];B[is]C[success again])
(;W[ns];B[jp];W[ko];B[ho];W[ip];B[gp];W[hq];B[fq])))
(;W[kp]C[white's shape is too bad for this];B[lp];W[kn];B[mp];W[ko];B[ps]))
(;B[ps]C[the squeeze fails];W[mp];B[ns];W[np];B[ko];W[lp];B[lq];W[kp];B[jp]
(;W[kn];B[kq];W[ko];B[km];W[io];B[ho];W[ip]C[the ladder doesn't work])
(;W[kq]C[huge mistake by white!];B[kr];W[kn];B[jq];W[ko];B[km];W[io];B[ho]C[like this, the ladder works])))
(;W[mp];B[os];W[np];B[ko];W[lp];B[lq];W[kp];B[kq];W[kn];B[jp];W[ko];B[km];W[io]
;B[hn]C[failure for white. black has connected under and lives. The cut at N2 does nothing.]))
(;B[os]C[this looks interesting, but fails];W[mq];B[mr];W[lq];B[lr];W[kr];B[kq]
;W[jr];B[kp];W[ko];B[io];W[ls];B[ns];W[qr]C[white has too many liberties, black dies]))
(;B[lp];W[ko];B[nq];W[nr];B[mr];W[mq];B[mp];W[lq];B[kp];W[lr]C[failure])
(;B[ko];W[mq]C[way too easy.]))