Its black to play here. But before we think of the move let us analyze the position.
Some positional aspects -
King safety: The black king relatively looks safe on g8 to the exposed white king on c1.
Space: White has a space advantage here having an advanced pawn on e5 and the rook having invaded the 5th rank.
Material: Equal
Pawn structure: Both have two pawn islands. Black has a queenside pawn majority which is generally an advantage. Opposite side castle always needs a pawn rush to the opponent’s king.
Piece activity: Again white’s piece activity seems a tad better than black’s as at first glance white has not developed against general principles and has completed development. On the other hand black’s rooks are yet to be co-ordinated and the knight on a6 looks out of place.
Piece co-ordination: As pointed out the black rooks are yet to be co-ordinated but this can be achieved with tempo maybe. On white’s side the bishop on d3 hinders the doubled rooks. The queen and rook seem to threaten the c5 pawn but that is well protected (and being on the king’s file white must not hurry in its capture unless black’s counter-play has been addressed)…but take a moment to see if there are any combinational threats that white can achieve?
Colour control: Black’s weakness is on the dark squares and white has the wrong bishop. Just replace the bishop on d3 with a dark squared bishop on e3…the intermediate Bh6+ is not possible and this improves the king safety largely. Also the dark squared bishop adds threat to c5 and makes the rook on d5 much stronger…allowing the co-ordination of the rooks too.
Synopsis: White’s king is exposed and there are no real threats for white, whereas black is lagging in development but is just behind in tempo. Is white’s better activity compensation enough for the loss of king safety? With black countering white’s lack of compensation this could be a problem.
What did black play?...if you spotted it…you are good…17…b5! But you are a genius if you see the continuation…black has to take advantage of this lack of king safety the focal point of black’s play if he intends to win the game. 18.Qh4 (Qxb5 allows Nc7 winning the exchange). 18…Nb4!!. The knight suddenly seems very strong…notice it is not forking…but it’s a triple attack on d5, c6 AND a2. Stop here and think can the knight get much stronger than just this triple attack? Should black continue with the exchange of on d3 or get greedy for the pawn on a2? What is the purpose of the knight on b4?
White has been up on development and his play revolves around taking advantage of this. 19. Bxg6…an excellent sacrifice aimed at weakening the black kingside. This also allows co-ordination of the rooks and invasion of the 7th rank with Rd7 and with Ng5 at the appropriate time seems to be a winning combination for white….but the knight on b4 stops all this…confused how? Read on…actually the sacrifice missed a critical point which you will realize at the end of this article. 19. Rd6 was a better move for white. 19…fxg6 20.Rd7 again in line with white’s original plan behind the sacrifice. Will this invasion really help white….this would have been a great move had the knight on b4 not been there. Ah! what can the knight do just Nxa2 which is met by Kb1 improving king safety? In the absence of the b4 knight black’s king side is under great pressure, the knight on f3 can jump into the attack and white would be winning here. 20…Qe8! this move is aimed at two aspects…the immediate is to prevent Qe7 with a mate threat that can only be compensated by sacrificing the rook 21…Bh6+ only prolongs the sacrifice. The only other move playable by black is Nc6. All other moves give white a clear advantage. So what is the other purpose of Qe8? To attack the e5 pawn for counter-play (not necessarily its capture).
White blunts this attack with 21. Re7 but the intermediate 21…Bh6+ taking advantage of the exposed king takes the steam out of Re7 so 22. Kb1 forced. I have all along been stressing on the importance of the knight on b4 only wanting you to notice an important factor – the control of the key c2 square. This control of the c2 square assumes great importance and the knight and the bishop (whose capture by Qxh6 would be a misadventure by white) have now co-ordinated well and have deftly put pressure on white’s king. Thus an earlier exchange of the knight for the miscoloured weaker bishop or for the pawn on a2 allowing a safer white king was losing if one could have noticed that the knight controls the c2 square and Kd1 exposes the king further and Kb1 allows a …………….you guessed it right back rank mate. What black played takes advantage of this critical weakness in white’s position 22…Rd8! (Rxd8 by white and white can resign to avoid further torture and embarrassment) 23. Rd6 Qc6! again taking advantage of the back rank mate…notice Rxc8 Rd1#. 24.a3 Rxd6 25.exd6 Qxd6 is black not losing the powerful knight that allowed all that was said above? The knight has served its purpose…with the free black queen and after 26. axb4 cxb4 27. Qe4 b3! all is lost for white with the invasion of the a-file by the queen with Qa6 followed by Qa2#, white resigned here.
This was a game between Belivasky and Kasparov in 1988…no wonder you found such powerful play by black.
