The usefulness of threats

[OHex]

Here's a littlegolem game where I found a good use for threats
that could not succeed by themselves. I have been the victim of
this strategem in the past, but I think this is the first time I
tried it myself. It felt weird making the preparatory moves.

I think the win is valid, but welcome comment.

(;FF[4]EV[hex.rt.2005.7.135]PB[***]PW[Kevin O'Gorman]
SZ[13]SO[http://www.littlegolem.com];
b[ab];r[gg];b[fg];r[ff];b[dg];r[dj];b[cj];r[ck];b[al];r[bk];b[ak];r[bj];
b[ej];r[ei];b[hh];r[if];b[fh];r[fi];b[hg];r[hf];b[gh];r[gj];b[ii];r[hk];
b[jj];r[il];b[kk];r[jm];b[ll];r[lk];b[kl];r[kj];b[jk];r[gd];b[fe];r[fd];
b[ge];r[hd];b[ed];r[ee];b[cf];r[ji];b[ij];r[ih];b[hi];r[cg];b[bi];r[df];
b[ah];r[aj];b[dh];r[bg];b[ag];r[bf];b[af];r[bd];b[id];r[ic];b[jc];r[he];
b[jg];r[ke];b[be];r[dc];b[resign])