This position is from Game 17 of the 1978 World Championship between Viktor Korchnoi, the challenger, and the World Champion, Anatoly Karpov. Karpov, playing Black, is threatening a back-rank mate with 39...Rc1#. Korchnoi could have prevented this by moving his g-pawn (but not the h-pawn because 39.h3 or h4 leads to 39...Rc1+ 40.Kh2 Nf1+ 41.Kg1 Nfg3+ 42.Kh2 Rh1#), providing an escape square for his king. In serious time trouble, Korchnoi played and resigned after 39...Nf3+ with the forced checkmate after 40. gxf3 Rg6+ 41. Kh1 Nf2# or 40.Kh1 Nf2#. Karpov went on to win the match and later beat Korchnoi again in 1981 in the "Massacre in Merano".