Kasparov: '17...Nf7 should lead to immediate disaster. But from this moment on, common sense must exit the stage, leaving limitless freedom for flights of fancy. The power of any piece is determined not by its relative value on the commonly used scale, but by the degree of its usefulness at any given moment.' With Black's next move, the game becomes a tactical slugfest.
17...b5. Black leaves the Knight on e5 en prise, but threatens ...b4, forking White's own Knights. Alburt's move 17...Bd7 is also interesting. 18.axb5. 18.fxe5 b4 19.Qb3 Nxg3 is good for Black. 18...axb5. Recaptures the Pawn and renews the threat ...b4. Kasparov: 'The first critical moment'. 19.Naxb5. If 19.fxe5, then 19...Bxe5 (not 19...b4? 20.Nc4, but 19...Nxg3 is worth considering) 20.Ne2 Nxg3 21.Nxg3 f4. Kasparov: 'Black has a strong attack. The White pieces on the Queenside have only static roles.'
