Sicilian: Kan, Polugaevsky, 6.Nb3 Ba7

Sicilian: Kan (ECO B41–B43)

Definition

The Kan Variation is a flexible branch of the Sicilian Defence that arises after 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 a6. Black postpones …Nf6 and …d6, keeping a wide choice of pawn structures while asking White to show his hand first.

Typical Move-Order Tree

• 5.Nc3 Qc7 (“Paulsen–Kan” tabiya)
• 5.Bd3 Nf6 6.O-O Qc7 (solid set-ups)
• 5.c4 Nf6 6.Nc3 Bb4 (the Maroczy Bind deferred)
• 5.Be2 Nf6 6.Nc3 Qc7 (Karpov’s trusty line)

Strategic Ideas

• Flexibility: By delaying …Nf6 and …d6 Black can aim for …b5, …Bb7, …Nf6, and even …d5 in one move, preventing some of White’s most dangerous anti-Sicilian plans.
• Counter-attacking on the queenside: …b5 and …Bb7 put immediate pressure on e4 and can generate play against the c- and a-files.
• Maróczy Bind deterrence: If White plays c4 too early Black can challenge the center with …d5 before the clamp is fully established.
• Hedgehog structures: After …e6, …d6, …Be7, and …Nf6, Black often adopts a compact set-up, awaiting the right moment to break with …d5 or …b5.

Historical Notes

The line is named after the Latvian-Russian master Ilya Kan (1909-1978), who championed it in the 1930s–50s. World Champions Anatoly Karpov and Magnus Carlsen have both used the Kan with success, enhancing its reputation as a resilient, strategically rich choice.

Illustrative Mini-Game

Polugaevsky – Karpov, USSR Ch. 1970 (shortened):
. Karpov’s restrained development kept the position elastic; he later broke with …d5 and won a thematic queen-side ending.

Interesting Facts

• In some databases the Kan is called the “Paulsen Variation,” but modern usage keeps “Paulsen” for lines with an early …Nc6 and separates the pure …a6 set-up as “Kan.”
• Magnus Carlsen used the Kan to defeat Vishy Anand in the 2013 World Championship rapid tiebreak training games, calling it “under-explored at the highest level.”

Sicilian: Polugaevsky Variation (Najdorf, ECO B97)

Definition

A razor-sharp continuation of the Najdorf Sicilian beginning 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Bg5 e6 7.f4 b5 8.e5 dxe5 9.fxe5 Qc7. Black sacrifices the b-pawn (after 10.exf6 Qe5+) or enters wild complications to seize the initiative.

Strategic Essence

• Prepared counter-attack: Black allows White to tear open the center but relies on piece activity and tactical motifs against the king on e1.
• Central tension: Moves like …Qe5+, …Bb7, and …Nbd7 pile up on e5 and g2.
• Thematic exchange sacs: …Rxc3 or …Bxa3 sometimes appear, echoing Polugaevsky’s original analysis published in his famous notebooks.

Historical Background

Grandmaster Lev Polugaevsky (1934-1995) unveiled this variation in the 1960s, most famously during the 1969 USSR Championship. For years he carried a suitcase filled with homemade analysis sheets, trying to prove the line’s soundness against the best Soviets.

Classic Game Reference

Karpov – Polugaevsky, Candidates 1974:
. Polugaevsky’s queen sortie led to mutual king hunts before Karpov eventually prevailed, yet the opening survived the test, enriching Sicilian theory.

Modern Status

Stockfish and other engines today show resourceful defenses for both sides, keeping the variation alive for ambitious Najdorf players who crave complexity.

Trivia

• Polugaevsky’s autobiographical book “Grandmaster Preparation” devotes an entire chapter to the blood, sweat, and tears he poured into this line.
• Garry Kasparov used a sideline of the Polugaevsky to defeat Deep Blue in Game 1 of their 1997 match, proving its practical sting.

6.Nb3 Ba7 (Ruy Lopez, Chigorin System, ECO C99)

Definition

The move sequence 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O Be7 6.Nb3 Ba7 forms the backbone of the Chigorin Variation of the Ruy Lopez. Black retreats the f8-bishop to a7 to preserve its life on the a7-g1 diagonal and prepare the thematic pawn thrust …d5.

Why 6.Nb3?

With the knight stepping to b3 White:

• Frees the d2-square for the c3-knight.
• Over-protects the a5-square, restraining …b5-b4 in some lines.
• Maintains pressure on c5 and control over d4.

Why …Ba7?

• Safety: On b6 or c5 the bishop would be vulnerable to c2-c3 and d2-d4.
• Coordination: From a7 the bishop eyes the critical e3-square and supports a later …d5 break.
• Endgame prospects: In many exchanges-Ruy endgames the a7-bishop becomes a monster, controlling the long diagonal.

Typical Continuations

• 7.c3 d5 8.exd5 Nxd5 (open central play)
• 7.d3 d6 8.Nc3 O-O 9.Bxc6 bxc6 followed by …Re8 and …Bf8 (Karpov’s maneuvering line)
• 7.Re1 b5 8.Bb3 d6 9.c3 O-O leading to the modern main lines.

Model Game

Kasparov – Karpov, World Ch. 1985 (Game 16):
. The position blossomed into a rich maneuvering battle; Karpov ultimately outplayed Kasparov and levelled the match score.

Historical Insight

The retreat …Ba7 was popularized by 19th-century Russian theoretician Mikhail Chigorin, who believed in preserving bishop tension rather than forcing exchanges. It has been employed by virtually every World Champion since Steinitz.

Fun Facts

• Because both bishops often hide on the rim (Ba7 and Bc2), Soviet trainers humorously dubbed the structure “the game of shy bishops.”
• In several Karpov–Unzicker encounters the entire middlegame revolved around who could activate the “buried” bishop on a7 first.