The Petrov Defense for Black

1.e4 e5 2.Nf3 Nf6

The Petrov Defense (also called the Russian Game) arises after 1.e4 e5 2.Nf3 Nf6: instead of defending the pawn on e5, you attack the pawn on e4 at once. It is one of the most solid answers to 1.e4 – world-class players rely on it when they want to stand safely with Black. One rule matters: after 3.Nxe5 you do not take back on e4 at once but play 3...d6 first, and only after 4.Nf3 4...Nxe4. The main line goes on with 5.d4 d5 6.Bd3, and you develop with Nc6, Be7 and short castling. Against 5.Nc3 you trade on c3, against 5.Qe2 you trade queens. Against 3.d4 you take on e4 and build a strong centre with d5; against 3.Nc3 you play the bishop to b4.

After 3.Nxe5 always d6 first: if Black takes on e4 at once, Qe2 attacks the knight – if it moves away, a discovered check by the knight on e5 wins the queen.
The knight on e4 is your outpost. Support it with d5 and only trade it when White harasses it with pieces.
Against c4 in the main line the knight jumps to b4 and attacks the bishop on d3 – after the trade White lacks his attacking bishop.
Against 5.Nc3 and White's long castling your position stays firm: trade on c3, develop with Be7, Nc6 and Be6, and your king is safe behind the pawns.
After the queen trade (against 5.Qe2) the endgame decides: bring your pieces out fast, the knight finds good squares via a6 and c7.