Petrov's Defense: Classical Attack, Mason Variation

1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.d4 d5 6.Bd3 Be7 7.O-O O-O

ECO C42

The Petrov's Defense: Classical Attack, Mason Variation is a chess opening line in the Petrov's Defense complex, reached after 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 catalogued under code C42 in the Encyclopaedia of Chess Openings (ECO).

The defining move O-O is chosen by Black on move 7.

Study this line with a grandmaster

This position is covered in the Petroff Defense course: a GM-authored repertoire you study move by move, then practice against a human-like AI opponent.

Every chess term used here is defined in the chess terms glossary. Browse all opening courses or the full ECO code index.