Caissa Codex
C42

Petrov's Defense: Classical Attack, Jaenisch Variation

Chess diagram: Petrov's Defense: Classical Attack, Jaenisch Variation after 8. c4

Type a move and press Enter: e4, Nf3, O-O, or from and to squares like g1f3 (e7e8q to promote). The board is also played with the mouse.

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Statistics from Lichess

48,598 games: White 47.2% / Draw 9.3% / Black 43.6%

The moves played next. Pick one to see it on the board.
Next moveGamesWhite / Draw / BlackW / D / B
33,79234K
7,6367,636
2,9472,947
2,6272,627
871871
569569
106106
1313

Rated Lichess games between players rated 1600 to 2500, from the Lichess opening explorer, updated Oct 30, 2026

Engine evaluation

+0.20 The position is about equal

Best play: 8... Nb4 9. Be2 O-O 10. a3 Nc6 11. Nc3 Nxc3 12. bxc3 Bf5 13. Re1

Stockfish 19, depth 30, after the line's last move. Scores are in pawns, from White's side.

Overview

Petrov's Defense: Classical Attack, Jaenisch Variation (ECO C42, Open Games) is a variation of Petrov's Defense: Classical Attack, Mason-Showalter Variation, reached after 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Nc6 7. O-O Be7 8. c4 (8 moves).

In 48,598 rated Lichess games between players rated 1600 to 2500, White won 47.2%, Black 43.6% and 9.3% were drawn. Black's most played move here is 8…Nb4, in 70% of those games.

It branches into 2 named variations; the most played are Petrov's Defense: Classical Attack, Chigorin Variation, Main Line and Petrov's Defense: Classical Attack, Chigorin Variation, Browne Attack.

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How to play against Petrov's Defense: Classical Attack, Jaenisch Variation

The most played answer, 8…Nb4, also scores best for Black: 49.0%, with Black winning 44.2% and White 46.2% of 34K games. Of the main answers, 8…O-O scores lowest: 43.9%. Stockfish's first choice is also 8…Nb4.

Main answers: those played in at least 5% of these games. Score: Black's wins plus half the draws, in rated Lichess games between players rated 1600 to 2500. How to play against other popular openings

Variations (2)

Other lines from the same position

Instead of 7. O-O Be7 8. c4, the position after Petrov's Defense: Classical Attack, Mason-Showalter Variation also goes on to:

Cite this page

Caissa Codex. “Petrov's Defense: Classical Attack, Jaenisch Variation (C42)”. Lichess data as of 30 Oct 2026. https://chesscodex.org/openings/petrovs-defense-classical-attack-jaenisch-variation

https://chesscodex.org/openings/petrovs-defense-classical-attack-jaenisch-variation