Two Knights: Morphy, Polerio, 6...c6

Two Knights Defense: Morphy (Polerio) Variation with 6…c6

Definition

The Morphy (also called Polerio) Variation with 6…c6 is a sharp line of the Two Knights Defense that arises after the moves 1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 d5 5. exd5 Na5 6. Bb5+ c6. Instead of interposing with 6…Bd7 or 6…c6 one move later, Black immediately hits the Bb5+ bishop while simultaneously challenging the white knight on g5 and opening the diagonal for the c8-bishop.

Typical Move Order

Standard sequence (algebraic notation):

1. e4 e5
2. Nf3 Nc6
3. Bc4 Nf6
4. Ng5 d5
5. exd5 Na5
6. Bb5+ c6

From here White’s most popular choice is 7. dxc6 bxc6, when the game often continues 8. Be2 h6 9. Nf3 Bd6 with a complex, materially balanced middlegame.

Strategic Ideas

• Central Counterstrike: By playing …c6 at once, Black prepares …cxd5 or …bxc6, seizing a strong pawn duo (c6–d5) to contest the center.
• Tempo Matters: 6…c6 forces the white bishop to decide its future square before White can complete development, creating tactical possibilities for Black based on …Nxd5 or …h6.
• Piece Activity vs. Structure: White often wins the d-pawn but spends time relocating pieces; Black accepts an isolated a-pawn (after …bxc6) yet gains active bishops and open lines.
• King Safety: Both sides delay castling; accurate timing of short-side castling (O-O) or even long-side (O-O-O for White) can decide the middlegame.

Historical Significance

Giulio Cesare Polerio (c. 1550–c. 1610) analyzed the idea of an early …c6 already in the late sixteenth century. Paul Morphy brought it to prominence in the nineteenth century, demonstrating its dynamic soundness against many contemporaries; hence modern literature often calls the line the “Morphy Defense” or “Morphy–Polerio Variation.”

Illustrative Game

Paul Morphy – Johann Löwenthal, London 1858 (casual)

Morphy sacrificed material to accelerate development; Black’s centralized pawns and open diagonals ultimately yielded a swift mating attack. The game helped convince analysts that 6…c6 is not only playable but a dangerous practical weapon.

Theoretical Status

• Engines rate the position after 7. dxc6 bxc6 roughly equal (≈0.00), but human play shows that both sides can go wrong quickly.
• Modern GMs such as Fabiano Caruana and Ian Nepomniachtchi have employed 6…c6 in rapid and blitz, trusting its surprise value and tactical richness.

Common Tactical Motifs

• Fork Trick: …Nxd5 ideas hitting c3/e3 squares after White plays c3.
• h-Pawn Chase: …h6 attacking the knight, leading to 8. Nf3 e4 with a discovered attack on f2.
• Diagonal Fire: The c8-bishop often lands on a6 or b7, creating pressure on e4 and g2.

Interesting Facts & Anecdotes

• Earliest Print: Polerio’s surviving manuscript “Ms. G 159” (c. 1590) contains the line up to move 8—over 250 years before Morphy!
• Morphy’s Speed: Contemporary reports claim Morphy could reproduce the full main line (through move 12) from memory in under 30 seconds while giving odds.
• Computer Age: AlphaZero’s self-play games have featured 6…c6 numerous times, often preferring it to the more theoretical 6…Bd7.

Practical Tips

• As White: after 7. dxc6 bxc6, consider 8. Be2 to break the pin on the knight and prepare d3 & O-O. Avoid 8. Bd3? e4! with a fork.
• As Black: if White plays 7. dxc6 bxc6 8. Be2, remember the flexible plan …h6, …Bd6, …O-O, and …Re8 targeting e4.
• Blitz Weapon: Many opponents still prepare only for 6…Bd7 or 6…b5, so 6…c6 can net quick time advantages over the board.