9. Petrosian System (4.a3) - Counterplay with 4...Ba6!
Black answers 4.a3 with ...Ba6 and, after 5.Qc2, brings the bishop back to b7 and hits d4 with ...c5. After 7.d5 exd5 8.cxd5 one must not take the d5 pawn: the line explains why and how to play the Benoni structure.
1.d4 Nf6 2.c4 e6 3.Nf3 b6 4.a3 Ba6 5.Qc2 Bb7 6.Nc3 c5 7.d5 exd5 8.cxd5
Move by move
- 1.d4 – White occupies the center with the d-pawn, protected by the queen, and frees the c1 bishop. This is the move that starts Queen's Gambit, Catalan and Nimzo-Indian games.
- 1...Nf6 – Black develops the knight toward the center and immediately prevents 2.e4. With Nf6 Black stays flexible: he can choose between the Nimzo-Indian, Queen's Indian, King's Indian or the Queen's Gambit Declined.
- 2.c4 – White gains space on the queenside and attacks the d5 square from a distance. White now threatens Nc3 and e4 to build a big pawn center.
- 2...e6 – Black opens the diagonal for the f8 bishop and prepares both d5 and Bb4. Compared with 2...d5, Black stays elastic: he waits to see whether White plays Nc3, which allows the Nimzo-Indian.
- 3.Nf3 – White develops the kingside knight instead of Nc3 and avoids the Nimzo-Indian: without the knight on c3, ...Bb4 can't pin anything, but White controls e4 less.
- 3...b6 – The Queen's Indian Defense: Black prepares Bb7 or Ba6 to control e4 and the light squares. Without a knight on c3, ...Bb4 would have no pin.
- 4.a3 – The Petrosian System: White prevents ...Bb4 and prepares Nc3 without being pinned. This way the c3 knight can support e4.
- 4...Ba6 – The bishop immediately attacks c4: with a3 White has spent a tempo and now has to defend the pawn with Qc2, Qa4, Nbd2 or b3.
- 5.Qc2 – The queen defends c4 and controls e4, the square White wants to conquer with Nc3 and e4. However, it leaves d4 with one defender fewer.
- 5...Bb7 – The bishop returns to the long diagonal: the white queen on c2 isn't on the ideal square, and from b7 the bishop controls e4 again.
- 6.Nc3 – White develops the knight and prepares e4, supported by queen and knight. It's the typical plan of the Petrosian System.
- 6...c5 – Black hits d4 before White plays e4: with the queen on c2 the d4 pawn is defended only by the f3 knight.
- 7.d5 – White pushes d5 to gain space and close the b7 bishop's diagonal. The d5 pawn is supported by the c4 pawn and the c3 knight.
- 7...exd5 – Black exchanges on d5 and opens the e-file. So White has to recapture, and the pawn that arrives on d5 will be advanced, far from White's other pawns.
- 8.cxd5 – White recaptures with the c-pawn and keeps an advanced pawn on d5. Careful: the d5 pawn seems to be en prise, but taking it with a piece is a mistake.
How to exploit the position
Benoni-like structure: White has the d5 pawn and more space, Black has the queenside majority. The d5 pawn must not be taken: after 8...Nxd5? 9.Nxd5 Bxd5 10.Qe4+ White gives check and wins the d5 bishop or the a8 rook.
- Play ...d6, ...g6, ...Bg7 and ...O-O: the bishop on g7 controls e5 and the long dark diagonal.
- Bring the b8 knight to a6 and c7, where it attacks d5 together with the b7 bishop and supports ...b5.
- Put the rook on e8 on the open file to curb the e4 push.
- Only when the d5 pawn is attacked more times than it is defended, and the e4-a8 diagonal is closed, can you take it.
Master tips
Don't take the d5 pawn
After 7.d5 exd5 8.cxd5 the d5 pawn looks free.