Chess games become more complex with the opening of files and diagonals as these are like paving roads for the pieces from both sides to infiltrate and invade. It is important for beginners and amateurs to think a lot before deciding to open a file or a diagonal as it might work in the opponent’s favour.

The game which follows is a classic example where Black needlessly opens a diagonal which a few moves later brings about his downfall as White’s bishop on this diagonal helps in weaving a few checkmating patterns.

White: Jonny Hector (2510) – Black: Steffen Pedersen (2415)
Oxford Grandmasters 'A', December 1998
French Defence
1.e4  e6 . The French defence which is a semi-open defence
2.d4 d5 3.Nc3 Nf6 4.Bg5 Bb4 5.e5 h6 6.Bc1. Back to square one? Usually White retreats to 6.Bd2 or 6.Be3
6...Ne4 7.Qg4 g6 8.Nge2 c5 9.a3 Bxc3+
Black can also think about retreating 9. ..Ba5 and maintaining the diagonal for the bishop and the continuation would be 10.b4 Nxc3 11.Nxc3 cxb4 a6 15.Nxc7+ Qxc7 16.0–0 Bd7 17.Bd2 Ne7 18.Qe2 Qb6 19.a4
10.bxc3. If  10.Nxc3 Nxc3 11.bxc3 Qa5 12.Bd2 Qa4 13.c4 Nc6 14.dxc5 Qxc2 15.Qf4 d4 16.Be2 Qf5 led to an unclear position in a previous game
 10...cxd4.
If 10...Qa5 11.f3! Nxc3 12.Bd2 cxd4 13.Nxd4 (13.Qxd4 Nxe2 14.Bxe2 Nc6 15.Qf4 Qc7 16.Bb5 Bd7) 13...Qc7 14.Qf4 Nd7 15.a4
And the knight has nowhere to go
 11.cxd4 Qc7 12.f3
He would like to dislodge the knight anchored at the centre
 12. ..Nc3.
He has no option of going elsewhere!
 13.Bd2 Nxe2 14.Bxe2 Bd7
If 14...Qxc2 15.Rc1 with clear advantage for White
 15.Bd3. White appears better
 15...Nc6 16.Rb1
Both players have not castled and White makes it clear that he would start attacking if Black castles on the queen side
16. ..0–0–0. And Black dares to castle on the queen side.
17.Qf4 g5 18.Qe3
Diagram 1
18. ..f6
A bad decision by Black1 He decides to open a crucial file which will work to White’s advantage as he has a bishop pair. If 18...Na5 19.Bb4 Nc4 20.Qe2 Bb5 21.0–0 Ba6 22.f4
19.exf6 Rdf8 20.0–0. The players have castled on opposite flanks and will start targeting the Kingsides
20. ..Rxf6 21.c4.
A strong advance!. It is White now who is interested in opening a file on the queen side. White’s pieces are better placed and can soon start attacking Black’s King
21...Rg8. If 21...dxc4 22.Bxc4 Na5 23.Bxa5 Qxa5 24.Rfc1 Kb8 25.Bb and White distinctly stands better
22.Rfc1 Be8 23.Be1
Once again retreating back to the back rank to hop onto a more promising diagonal to target Black’s King
23...Bg6 24.Bg3 Qf7 25.Be5 Bxd3 26.Qxd3 Rfg6 27.cxd5 exd5 28.Qb5
The Queen spearheads the attack and things have become difficult for Black with all of White’s pieces firmly gunning for the King
28. ..Rd8. If 28...g4 29.f4 g3 30.h3
29.Qa4 a6 30.Rb6 Qd7
If 30...Qe6 31.Rcb1 Rd7 32.Rxa6 bxa6 33.Qxc6+
31.Qxa6
Sacrificing the queen as a final finishing touch to set up various checkmating traps. Black resigned as the position is hopeless
Diagram 2
White to play and win
1.Rh1+ Kg8 2.Rh8+ Kxh8 3.Rh1+ Kg8 4.Rh8+ Kxh8 5.Qh1+ Kg8 6.Qh7 checkmate.

Diagram 1

Diagram 2