Petrov's Defense: what should White play?

In the classical position of Petrov's Defense (ECO C42), White's most critical and statistically favored try is d4, staking an immediate claim in the center while Black's e4 sits exposed. Evaluated by engines at +0.39, this central advance is chosen in 42.1% of recorded games (1.83M recorded) and yields White a 53.8% score. By seizing space and challenging Black's central coordination immediately, White establishes long-term pressure before Black completes kingside development.

The Classical Main Line with d4

Advancing with d4 directly addresses the center and prepares fluid development for White's light-squared bishop. In the engine main line d4 d5 Bd3 Nc6 O-O Be7, White challenges the knight on e4 by targeting it with the bishop from d3 after castling. Black bolsters the knight with a symmetric central pawn push, leading to solid, positional maneuvering where White retains a modest space advantage.

Nimzowitsch's Nc3 Alternative

White's second most common choice is Nc3, occurring in 30.7% of games (1.33M recorded) with an engine evaluation of +0.26 and White scoring 54.9%. This line, often associated with rapid development, invites immediate exchange through Nc3 Nxc3 dxc3 Be7 Be3 Nd7. By recapturing toward the center with the d-pawn, White opens lines for the queen and bishops to facilitate smooth queenside coordination.

Quieter Options: d3 and Bd3

Players seeking less complex structures may opt for d3, seen in 21.2% of games (919K recorded, scoring 49.9%), which immediately drives Black's knight away. The engine evaluates d3 at +0.11, illustrated by the continuation d3 Nf6 d4 d5 Bd3 c5. Similarly, developing immediately via Bd3 represents 4.9% of games (211K recorded) with a +0.10 evaluation, flowing into Bd3 d5 O-O Be7 Re1 Nf6. Both approaches yield symmetrical, balanced middlegames with minimal theoretical risk.