Nimzo-Indian: Classical Variation (4...O-O 5.a3)
Nimzo-Indian Defence – Classical Variation
4…O-O 5.a3 Bxc3+ 6.Qxc3 b6 7.Bg5 Bb7 8.e3
Definition
This line is a branch of the Classical Variation of the Nimzo-Indian Defence, which arises after:
1.d4 Nf6 2.c4 e6 3.Nc3 Bb4 4.Qc2 O-O 5.a3 Bxc3+ 6.Qxc3 b6 7.Bg5 Bb7 8.e3
• Classical Variation (4.Qc2): White protects the knight on c3 with the queen, avoiding doubled c-pawns.
• …O-O (move 4): Black castles immediately, delaying the choice of what to do with the bishop on b4.
• 5.a3: White forces the bishop to resolve the pin; Black normally exchanges on c3.
• 6…b6: Black adopts the “Hübner plan” (…Bb7 and …d6) to develop the dark-squared bishop and prepare central breaks.
• 7.Bg5 Bb7 8.e3: White pins the f6-knight and prepares a solid development with Nf3, Bd3 and O-O, while Black readies …d5 or …c5.
Strategic Themes
- Imbalance of bishop pairs: After …Bxc3+ White owns the pair of bishops, but suffers a slightly weakened queenside pawn structure (doubled c-pawns are avoided, yet the isolated a-pawn can become a target).
- Flexible pawn breaks: Black keeps both …d5 and …c5 in reserve. The move …b6 supports …Bb7 and often …d5, striking at e4 once White pushes that pawn.
- Piece activity vs. structure: White intends to exploit the bishop pair in a long game, often expanding with f3 & e4. Black looks for dynamic counterplay in the center before the bishops spring to life.
- The Bg5 Pin: With 7.Bg5 White irritates the knight on f6, discouraging an early …Ne4 since the knight would be tactically unstable.
- Minor-piece maneuvering: Typical Black plans involve …d6–…Nbd7–…Re8–…e5 or …c5. White may reroute the knight via e2–g3 or f3–d2–e4 to support central pushes.
Historical Significance
The 6…b6 scheme was popularised by grandmasters Wolfgang Hübner and Lajos Portisch in the 1970s. Anatoly Karpov employed the line repeatedly as White, trusting his end-game skill with the bishop pair. Garry Kasparov and later Viswanathan Anand have explored Black’s dynamic potential. Modern engines show the variation to be fully playable for both sides, keeping it a main-line battleground even in elite events.
Typical Plans and Ideas
- White:
- Develop normally: Nf3, Bd3, O-O, Rd1.
- Break with e4 (supported by f3 or Rd1).
- Exploit the g2–a8 diagonal after a future d5 break opens lines for the c3-bishop.
- Prepare a central pawn roller: f3–e4–e5.
- Black:
- Counter-punch with …d5 or …c5, hitting the white center.
- Transfer the knight to d7/e4 after …d6.
- Target the a-file weaknesses (a3 pawn) with …Ba6 or …Bc6.
- In some cases exchange dark-squared bishops with …Ba6 to reduce White’s pair.
Illustrative Miniature Game
Karpov – Portisch, Linares 1991 (simplified excerpt):
The game demonstrates a typical bishop-pair end-game in which Karpov slowly converted the small structural edge into a win after mass exchanges.
Notable Modern Encounters
- Carlsen vs Aronian, Candidates 2013 – A deep theoretical duel where Carlsen (White) chose 9.Nf3 and gained a slight pull.
- Kasparov vs Deep Blue, 1997 (Game 5) – The machine essayed 6…b6; Kasparov deviated later, but the opening highlighted computer confidence in the line.
- Gelfand vs Anand, WCh 2012 (Game 8) – Anand equalised comfortably with the 6…b6 scheme, helping him retain his title.
Interesting Facts & Anecdotes
- The move 6…b6 originally had the reputation of being slightly passive until Hübner unveiled fresh ideas in the late 1960s, rehabilitating it at top level.
- Because the black bishop often lands on a8 after …Bb7-a8, some grandmasters jokingly call it the “Spanish bishop” – enjoying a long holiday before returning to the game when the center finally opens.
- Engines show near-perfect equality, yet human grandmasters still choose the line when they wish to avoid the razor-sharp 6…c5 or 6…d5 main lines and steer the game into a rich positional struggle.
Quick Reference
ECO Code: E38
Key Tabia after 8.e3: