King's Indian: Accelerated Averbakh, 5...O-O

King's Indian: Accelerated Averbakh, 5…O-O

Definition

The Accelerated Averbakh is a sub-variation of the King's Indian Defense (ECO code E73) that arises after the following ten-ply sequence:

Because Black castles one move earlier than in the “classical” Averbakh (5…e5 6.Bg5), the line is dubbed “Accelerated.” White’s 5.Be2 keeps options flexible, while Black’s quick …O-O prioritises king safety and preserves central tension.

Typical Move-Order & Branches

• 6.Bg5 – the original Averbakh idea, pinning Nf6.
• 6.Nf3 followed by 7.O-O – a more restrained set-up.
• 6.h4!? or 6.f4!? – modern, aggressive tries to seize space.
• After 6.Bg5 Black can choose among:
  • 6…c5 – Benoni-flavoured central fight.
  • 6…Nbd7 / 6…Na6 – flexible development keeping …e5 in reserve.
  • 6…e5 – reverting to Classical KID structures.

Strategic Themes

• Black
  • Maintains a compact centre and decides when to strike with …e5 or …c5.
  • Early castling lets the f8-rook rapidly join the fray via …Re8 or …f5.
  • Typical plans include pawn breaks (…e5, …c5, …b5) and piece pressure on the long diagonal.
• White
  • Uses Bg5 or h2-h4 ideas to pin and harass the knight on f6.
  • Aims for space with f2-f3, g2-g4 or the central thrust d4-d5.
  • Because Black’s …e5 is delayed, White may choose a slower, positional build-up.

Historical Notes

The Averbakh System is named after Soviet grandmaster and endgame authority Yuri Averbakh, who popularised the 6.Bg5 idea in the 1950s. The accelerated form with 5…O-O was investigated a little later, gaining popularity in the 1960s after appearing in games by Petrosian, Spassky, and others. Modern elite players such as Vladimir Kramnik, Teimour Radjabov, and Leinier Domínguez have kept the line theoretically relevant.

Illustrative Mini-Line

One frequently cited reference position comes after:

The position features:

• A locked centre (pawns on d5/d6 & c4/c5).
• White’s light-squared bishop probing on f4.
• Black readying …Na6–c7 or …b5 to undermine White’s queenside.

Notable Games

1. Spassky – Petrosian, World Championship Match (10), Moscow 1966
   The challenger used 6.Bg5 and achieved a lasting space advantage, though the world champion steered the game to a draw with accurate defence.
2. Kramnik – Topalov, Dortmund 1999
   Kramnik’s subtle manoeuvring with 6.Nf3 and 7.O-O showcased how quiet development can restrain Black’s counterplay and eventually yielded a technical end-game win.
3. Nakamura – Radjabov, Wijk aan Zee 2011
   A modern heavyweight clash in which Black uncorked the sharp …c6 & …d5 break, demonstrating the line’s latent dynamism.

Interesting Facts & Anecdotes

• Despite lending his name to the variation, Yuri Averbakh later remarked that he preferred other defences as Black because “it is too difficult to prove full equality against one’s own system.”
• Computers initially assessed the Accelerated Averbakh as slightly better for White, but modern engines armed with ideas such as …Na6–c7–e8–f5 now regard the position as roughly balanced.
• The structure often transposes into Benoni-type setups, allowing players to “mix openings” and avoid opponent preparation—a favourite practical weapon of blitz specialists on sites like Hikaru Nakamura.

Why Study This Line?

For King’s Indian players it offers a safe, theory-light route to familiar middlegames; for Queen’s pawn players, it serves as an instructive case study in maintaining central space and exploiting a lead in development. Understanding the Accelerated Averbakh deepens one’s grasp of tension-based strategy, flexible move-orders and the eternal struggle between space and dynamism.