Petrov's Defense: Classical Attack, Mason-Showalter Variation is a chess opening with the ECO code C42, part of the Petrov's Defense family. It goes 1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Nc6. White opens with 1. e4 (the king's pawn) and Black answers 1... e5. After 12 moves it is White to move. The lesson on the board explains every move of the line and lets you play it yourself; it is free.
The moves
1. e4 – White plays the pawn to e4
1... e5 – Black plays the pawn to e5
2. Nf3 – White plays the knight to f3
2... Nf6 – Black plays the knight to f6
3. Nxe5 – White takes on e5 with the knight
3... d6 – Black plays the pawn to d6
4. Nf3 – White plays the knight to f3
4... Nxe4 – Black takes on e4 with the knight
5. d4 – White plays the pawn to d4
5... d5 – Black plays the pawn to d5
6. Bd3 – White plays the bishop to d3
6... Nc6 – Black plays the knight to c6
In chessGM's opening book this position continues with 7. O-O.
About the Petrov's Defense
After 1.e4 e5 2.Nf3, Black counterattacks e4 with 2...Nf6 instead of defending e5. It is symmetrical and very solid.
After 3.Nxe5, do not copy with 3...Nxe4?; first play 3...d6, then take.
The trap: 3...Nxe4? 4.Qe2 and the pin on the e-file wins material.
Black aims for quick development and a safe, equal position.