Sequence of captures very important

Sometimes, moves which look very natural or obvious in certain positions in a game of chess can be the most dangerous or fatal. While trading or exchanging pieces, it is very important to check out which piece has to be captured first and whether it is correct to capture it with a pawn, a minor(knight and bishop) piece or a major piece(rook and queen). In fact the sequence of captures is very important and it is what distinguishes it from being a good combination to a faulty one.

In the game which follows, Black is not in a very comfortable position but can definitely hang on to pose a stiffer defence. On the 25th turn Black errs in deciding on a capture and his game falls apart totally.

White: John Nunn (2585) – Black: Tukmakov Vladimir (2570)
Lugano, 1986
Sicilian Defence
 1.e4 c5
The Sicilian Defenc which is a considered a sharp response to the King Pawn Opening
2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 Nc6 6.Bc4 Qb6 7.Nb3 e6 8.0–0 Be7
Opening theoretical moves
9.Bg5 Ne5
If 9...a6 10.Bxf6 gxf6 11.Qh5 Nd4
10.Be2 Bd7 11.Kh1
Moving out of the diagonal which the Black queen has occupied
11. ..Ng6
11...0–0 12.f4 Ng6 13.e5 dxe5 14.Bxf6 Bxf6 15.Qxd7  and the White queen infiltrates onto the seventh rank which sort of ties Black’s pieces
12.Be3 Qc7 13.f4
A good advance!
13. ..0–0
Black decides to castle immediately
14.Qe1 14...Rfe8 15.Rd1
The rooks are taking up positions. However White appears a trifle better here
15. ..Bc6
Here perhaps White would have been better off playing 15...Bf8.
16.Bf3 d5 17.e5 Ne4 18.Nd4 Nxc3
This is more or less forced since White was threatening to win a pawn with 19.Bxe4 dxe4 20.Nxc6 Qxc6 21.Bd4 Rac8 22.Rd2 and if 18...Bb4 then19 Nxd5
19.Qxc3 Rac8
Doubling on the file
20.Qe1 Bd7 21.Qg3 Qb6
Black sees the vulnerability of the b2 pawn and hope to grab it but in the process places his queen in direct diagonal where White has already posted his bishop. He should have seriously considered the possibility  21...Qa5  after which he could have put up some better defence
22.f5
Targetting the King side as his pieces are better placed there.
22. .. exf5
If 22...Bh4 23 Qh3 exf5 24 Bxd5 Rxe5 25 Bxf7+ Kh8 (or  25...Kxf7 26 Nxf5 with a winning attack) 26 Bxg6 Qxg6 27 Bf4 and White  should win in this position.
23.Bxd5 Bh4 24.Nxf5
Making things interesting with some flashy fireworks. White can win simply with  24 Qh3  without any problems
24...Bxg3 25.Bxb6
Trading queens amidst all tension
Diagram 1
25. ..axb6
This looks like the most natural move but it loses immediately. The position is bad for Black and perhaps the best try here would have been 25...Bxe5 26 Bxa7 and the onus would be on White to nurse the extra pawn to victory
 26.Nd6
The killer punch! Black has no reply for this and his game collapses like a pack of cards If 26...Bxe5 27 Bxf7+ Kh8 28 Bxe8 Rxe8 29 Nxe8 Bxe8 30 Rd8 or 26...Bh4 27 Bxf7+ Kh8 28 Bxe8 Rxe8 29 Nf7+ and 30 Rxd7. Black resigned in this position.
Diagram 2
White to play and win
 1.Qxh4+
A superb queen sacrifice!
1.   ..Bxh4 2.Bg7+ Kh5 3.g4 checkmate.