Petrov's Defense: Classical Attack, Mason Variation (C42)

The Classical Attack, Mason Variation is a variation of the Petrov's Defense, catalogued as ECO C42. The line runs 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 7. O-O O-O, reaching the position shown below after 14 half-moves.

Both sides have pawns in the centre (White on d4, Black on d5). Development is level at two minor pieces each. It is White to move after seven moves. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank; the e-file file is fully open.

On the Petrov's Defense generally: A symmetrical defense known for its solidity. Black mirrors White's moves in the opening.

You can play through this variation move by move in your browser — Learn mode walks the line with an explanation at each step, and Drill mode replays it from memory so you find out whether you actually know it. No account is required.

Position characteristics

• Contested centre
• Same-side castling
• Open file

Related Petrov's Defense lines

• Classical Attack, Marshall Trap
• Classical Attack, Marshall Variation
• Classical Attack, Marshall Variation, Chinese Gambit
• Classical Attack, Maróczy Variation
• Classical Attack, Mason-Showalter Variation
• Classical Attack, Staunton Variation
• Classical Attack, Tarrasch Variation
• Cochrane Gambit, Bishop Check Line
• Classical Attack
• Classical Attack, Berger Variation
• Classical Attack, Chigorin Variation
• Classical Attack, Chigorin Variation, Browne Attack

See all 30 Petrov's Defense variations →

Frequently asked questions

What are the moves of the Classical Attack, Mason Variation?

The Classical Attack, Mason Variation goes 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 7. O-O O-O. It is a variation of the Petrov's Defense and is catalogued as ECO C42.

What is the ECO code for the Classical Attack, Mason Variation?

The Classical Attack, Mason Variation is ECO C42. ECO codes group openings by their move order, so nearby codes cover closely related lines of the Petrov's Defense.

Is the Classical Attack, Mason Variation good for Black?

Stockfish evaluates the position after 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 7. O-O O-O at +0.41 at depth 18, which is a slight pull for White, within normal opening margins. Engine evaluation is only a starting point — at club level the practical value of a line is mostly about whether you know its plans better than your opponent does.

What kind of position does the Classical Attack, Mason Variation lead to?

Both sides have pawns in the centre (White on d4, Black on d5). Development is level at two minor pieces each. It is White to move. Both kings have castled kingside, so play tends to shift to the centre and the opposite flank; the e-file file is fully open.