Sicilian Kan: 5.c4 Nf6 6.Nc3 Bb4

Sicilian Kan: 5.c4 Nf6 6.Nc3 Bb4

Definition

The line 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 a6—known as the Sicilian Kan (or Paulsen)—is a flexible variation of the Sicilian Defence in which Black postpones …Nc6 and …d6 in favor of the subtle …a6 and …e6 pawn structure. The specific sequence 5.c4 Nf6 6.Nc3 Bb4 introduces a sharp sub-variation:

1. e4  c5
2. Nf3 e6
3. d4 cxd4
4. Nxd4 a6
5. c4 Nf6
6. Nc3 Bb4

Here, Black develops the queen’s bishop to b4, pinning the c3-knight and pressuring e4 while retaining a compact, resilient pawn structure.

Strategic Themes

• Central Tension: White’s pawn on c4 forms a Maroczy-like grip, restricting …d5. Black responds by undermining the center with piece pressure rather than immediate pawn breaks.
• Piece Play vs. Space: White enjoys extra space, but Black’s pieces have clear targets—specifically the e4 pawn and the knight on d4 after …Nxe4 or …d5.
• Flexible Pawn Breaks: Black may choose …d5 (striking in the center), …b5 (expanding on the queenside), or even …e5 after adequate preparation.
• Structural Imbalance: The pin on c3 often entices White to play 7.Bd3 or 7.Qd3. If 7.e5, the game can transition into a Scheveningen-style structure.

Typical Continuations

Two of the most common replies after 6…Bb4:

• 7.Bd3 Nc6 8.Nxc6 dxc6 — Black accepts doubled c-pawns but gains the bishop pair and quick play against White’s center.
• 7.Qd3 Nc6 8.Nxc6 dxc6 9.Qxd8+ Kxd8 — Leads to simplified positions where the Black king is centrally placed but safe in an open endgame.

Historical & Practical Significance

The Kan is popular among players who appreciate flexibility and are willing to concede space for a dynamically sound structure. Grandmasters such as Carlos Torre, Vlastimil Jansa, and more recently Alexei Shirov and Fabiano Caruana have experimented with this exact pin-setup. The line received theoretical attention when John Nunn employed it successfully during the 1980s, revitalising Black’s options against the Maroczy Bind.

Illustrative Game

Akopian – Shirov, Tilburg 1997
Shirov chose 5.c4 Nf6 6.Nc3 Bb4 and later achieved …d5, equalising and eventually winning a rich tactical battle. The game showcases Black’s idea of pressuring e4 before striking in the center.

Practical Tips

• For White
  • Safeguard the e4 pawn—consider f3, Bd3, or Be2 depending on move order.
  • Timely castles kingside; do not allow …Nxe4 tactics exploiting the pin on c3.
  • If pursuing a Maroczy structure, maintain pieces; exchanges help Black free his game.
• For Black
  • Use …Bb4 to force concessions—doubles on c6 are acceptable if you gain quick counter-play.
  • Be alert to breaks: …d5 (central) or …b5 (queenside) according to piece placement.
  • After …Nc6 and exchanges on c6, guard the c-file; the open b8–h2 diagonal can favor the g7-bishop in related lines.

Interesting Facts & Anecdotes

• The move 5.c4, once considered the “Marcozy’s Revenge” against the Kan, was revitalised for Black by American GM Larry Kaufman, who showed the strength of 5…Nf6 6.Nc3 Bb4.
• Although the Kan is sometimes called the “Paulsen” (after Louis Paulsen), the modern setup with …a6 came into vogue thanks to Swedish GM Gideon Ståhlberg in the 1940s.
• The line appeals to engines: modern neural-net evaluations (e.g., Leela) often hover around 0.00, proving its resilience at the highest analytical depths.

Summary

The sub-variation 5.c4 Nf6 6.Nc3 Bb4 in the Sicilian Kan offers Black a nimble, piece-oriented way to fight against White’s spatial advantage. Its blend of solidity and latent dynamism has earned it a permanent spot in grandmaster repertoires and remains a valuable weapon for players seeking fresh, flexible Sicilian territory.