Along with Nimzowitsch principles (mainly prophylaxis - preventing opponent's offensive capabilities), Petrosian developed his own strategy where all his pieces were kept on white squares and controlled the black squares from there. Petrosian kept a lot of pawns on board and exchanged his bishop (usually white bishop or both bishops) with opponent's knights quite often. After this, his knights used to rule the black squares. This strategy was very useful for white against Kings Indian defence and in english opening.
Petrosian was called "Iron Tigran" because of his consistent ability to avoid defeat. As Black, he preferred to play closed openings in Sicilian Defence, Najdorf variation and French Defence. As white player, he often played the English opening.
Exchange Sacrifice (Giving rook for opponent's bishop or knight) just for the sake of quality of position: Kasparov, who later induced this idea in his own games describes Petrosian's style in these words:
" Petrosian introduced the exchange sacrifice for the sake of 'quality of position', where the time factor, which is so important in the play of Alekhine and Tal, plays hardly any role. Even today, very few players can operate confidently at the board with such abstract concepts. Before Petrosian no one had studied this. By sacrificing the exchange 'just like that', for certain long term advantages, in positions with disrupted material balance, he discovered latent resources that few were capable of seeing and properly evaluating."
Petrosian's Opening Innovations:
1. Petrosian System for White against King's Indian Defence:1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. Nf3 O-O 6. Be2 e5 7. d5 (closing the centre early in the game). White plays Bg5.
2. Petrosian System for White against Queen's Indian Defence:1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.a3 (preventing Bb4). This system was later used by Kasparov to defeat several grandmasters.
3. Petrosian System for White against Grunfeld Defence:1.d4 Nf6 2.c4 g6 3.Nc3 d5 4.Nf3 Bg7 5.Bg5
4. Petrosian System for Black in French Defence:1.e4 e6 2.d4 d5 3.Nc3 Bb4 4.e5 Qd7
5. Petrosian - Smyslov variation for Black in Caro-Kann Defence:
1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nd7
Example Game 1: Petrosian beats Spassky's Torre Attack (Please click mouse on the first move and then either arrow key on keyboard or mouse click on next moves to see game on the board. Enjoy and comment !)
Example Game 2: Petrosian beats Spassky's Kings Indian Defence
Example Game 3: Petrosian beats Suetin's Kings Indian Defence with his Deep Prophylaxis method
1. Gary Kasparov, My Great Predecessors Part III (Petrosian & Spassky), Everyman Chess
2. Chessbase DVD "The Secret Weapons of World Champions" by Mikalchishin