Last week’s puzzle was taken from Jan Timman’s new book The Unstoppable American: Bobby Fischer’s Road to Reykjavik (New in Chess 2021): my review will be published on British Chess News shortly.
This was from Gligoric – Fischer (Siegen Ol 1970). Gligoric played Kf3 here, and, after some further inaccurate moves, lost the game.
Instead, he could have gained a winning positional advantage by playing the (fairly obvious, I would have thought) 39. Nb1!, with the idea of Nd2, Nc4 and Kg4.