Editing Tigran Petrosian (section)

=== Contributions to opening theory ===

{{Chess diagram small
|tright
|[[King's Indian Defence|KID]], Petrosian System
|rd|nd|bd|qd|  |rd|kd|
|pd|pd|pd|  |  |pd|bd|pd
|  |  |  |pd|  |nd|pd|
|  |  |  |pl|pd|  |  |
|  |  |pl|  |pl|  |  |
|  |  |nl|  |  |nl|  |
|pl|pl|  |  |bl|pl|pl|pl
|rl|  |bl|ql|kl|  |  |rl
|1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.d5
}}

Petrosian was an expert against the [[King's Indian Defence]], and he often played what is now known as the Petrosian System: 1.d4 Nf6 2.c4 g6 3.Nc3 Bg7 4.e4 d6 5.Nf3 0-0 6.Be2 e5 7.d5.<ref>[http://www.chessgames.com/perl/chessopening?eco=E93 King's Indian, Petrosian System] on ChessGames.com</ref><ref>[https://www.chess.com/openings/Kings-Indian-Defense-Petrosian-Variation King's Indian Defense, Petrosian Variation] on Chess.com</ref> This variation closes the centre early in the game. One of the tactical ideas for White is to play Bg5, pinning Black's knight to his queen. Black can respond by either moving his queen (usually ...Qe8) or by playing ...h6, though the latter move weakens Black's kingside [[pawn structure]].{{sfn|Gufeld|Schiller|2000|p=140}} Two of Black's responses to the Petrosian Variation were developed by grandmasters [[Paul Keres]] and [[Leonid Stein]]. The Keres Variation arises after 7...Nbd7 8.Bg5 h6 9.Bh4 g5 10.Bg3 Nh5 11.h4, and the Stein Variation begins an immediate queenside offensive with 7...a5.{{sfn|Gufeld|Schiller|2000|pp=140–42}}

The [[Queen's Indian Defence]] also has a variation developed by Petrosian: 1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.a3,<ref>[https://www.chess.com/openings/Queens-Indian-Defense-Petrosian-Variation Queen's Indian Defense, Petrosian Variation] on Chess.com</ref> with the idea of preventing ...Bb4+. This system received much attention in 1980 when it was used by the young [[Garry Kasparov]] to defeat several grandmasters. Today the Petrosian Variation is still considered the most pressing variation, with the greatest score in Master games.<ref>{{Cite web|url=https://www.365chess.com/opening.php?m=7&n=21&ms=d4.Nf6.c4.e6.Nf3.b6&ns=7.14.11.33.21.21|title=E12: Queen's Indian defence – 1. d4 Nf6 2. c4 e6 3. Nf3 b6 – Chess Opening explorer|website=www.365chess.com}}</ref>

Other Petrosian variations can be found in the [[Grünfeld Defence]] after 1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3 Bg7 5.Bg5,<ref>[https://www.chess.com/openings/Grunfeld-Defense-Petrosian-System Gruenfeld Defense: Three Knights Variation, Petrosian System] on Chess.com</ref> and the [[French Defence]] after 1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.e5 Qd7.<ref>[https://www.chess.com/openings/French-Defense-Winawer-Advance-Petrosian-Variation French Defense: Winawer Variation, Petrosian Variation] on Chess.com</ref> Some authorities refer to a variation of the [[Caro–Kann Defence]] with his name, along with former world champion [[Vassily Smyslov]]: the Petrosian–Smyslov Variation, 1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Nd7.{{sfn|Karpov|Beliavsky|1994|p=needed}}