Timely exchange of pieces is very significant

Timely exchange of pieces is very significant

In the game which follows, White is positionally better but black has some chances of trying for counter play. However Black decides and initiates a few exchanges, making things easy for . There is a point in the game where Black has two pieces hanging but White wraps up the game with a queens sacrifice, missing out on a much easier win.
 White: Dirk Rosenthal (2352) – Black: Matthias Schurade (2360) Oberliga Nord, 1999 Sicilian Defence

1.e4 c5
The Sicilian defence
 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 e6 7.f4
Sharp continuation by White
 7. ..Nbd7 8.Qf3 Qc7 9.0–0–0
Making things interesting by castling on the queen-side
 9. ..b5
Black immediately starts rolling his pawns on the queen-side
Ditto from White on the King side
 10. ..Be7 11.Bxf6 Nxf6 12.g5 Nd7 13.f5
White is keen on breaking into the King side
 13. ..14.f6 gxf6 15.gxf6 Bf8 16.Rg1 h5
If 16...b4 17.Nd5 exd5 18.exd5 Bd7
Till now, the players were following a previous game but now White makes a new move. If  17.Rg7 b4
Black is trying to attack the King , led by his pawns
White decides to sacrifice the knight
 18. ..exd5 19.exd5 Bg4 20.Re1+ Kd8 21.Qf4 Bh6
Black has a bishop pair and would like to control things even though his king has not been able to castle

 Diagram 1

 22. ..Re8
A bad move! With an exposed King and pieces which look uncoordinated, Black could have taken time off to post his pieces onto better squares rather than force exchanges.
White is more than ready to swap pieces
 23. ..Kxe8 24.h3
A clever move! Capitalizing on the vulnerability of the Black King! White is now threatening 25.Rg8+
 24. ..Ne4 25.Qe1 Making things difficult for Black!. Now he has a hanging knight and a bishop
 25. ..Kd7  He hardly has any choices! If 25...Kf8 26.Qxe4 Re8 27.Ne6+ fxe6 28.Qg6 Be3 29.Rg2 (29.hxg4 Bxg1 30.Qh6+ Kg8 31.dxe6 Rxe6 32.Bc4) 29...Qf7 30.Qxf7+ Kxf7 31.hxg4
 26.hxg4 Going for the bishop first! If 26.Qxe4 Re8 27.Ne6 Bxe6
 26...Nd2+ 27.Ka1 Re8 28.Bh3
Not the best move! White could have gained clear cut advantage after 27.Bxa6 Rxe1+  28.Rxe1
 28. ..Rxe1+ 29.Rxe1 Qd8 If 29...Qc5 30.Re7+ Kc8 31.g5+ Kb8 32.Nc6+ Ka8 33.Re8+ Kb7 34.Rb8+ Kc7 35.Rc8+ Kb6 36.Rb8 with just a slight edge for White
 30.Nc6 Qf8 31.Re7+ Infiltrating in a very strong manner!
 31. ..Qxe7  White hardly has any choice!  32.gxh5+ Qe6 33.dxe6+ fxe6 34.Nd4 Ne4 35.Bxe6+ Ke8 36.Nf5 Two of White’s passed pawns on the King side are making life miserable for Black  36. ..Bf4 37.f7+ and Black resigned in this hopeless position.

Diagram 2

White to play and win 1.f7+ Kxf7 If 1...Rxf7 2.Qh8 checkmate
 2.Rxb7 Rxb7 3.Qd5+ Re6 4.Qxb7+ Re7 5.Qd5+ Qe6  and White wins.