13.Bxf5

Korchnoi considered this 'probably the decisive mistake', and suggested 13.Nc1 instead. If then 13...Bxd3 14.Nxd3 Re2 15.Na3. This variation explains why Korchnoi considered 11...Qe7 more accurate than 11...Re8. If the Queen were on e7, Black would be able to play 14...Qe2, when 15.Na3 would leave the Knight on d3 unprotected.

Next move: 13...Rxe2