Philidor Defense: what to play after Bg4?

In the Philidor Defense after Black develops the light-squared bishop to g4 and pins the knight on f3, White's highest-evaluated choice is d4 (evaluated at +0.95). Striking immediately in the center allows White to contest space while Black's queen is prematurely committed to e7. White scores 52.8% across 3.7K recorded games with this central advance, though quiet developing setups remain sound alternatives.

Direct Central Confrontation with d4

Although h3 is the most common human choice at 53.4% of recorded games (17K games, scoring 53.0%), d4 represents the most ambitious path against Black's passive setup. Played in 11.7% of games, this pawn break challenges the e5 outpost and opens lines for White's pieces. An illustrative continuation demonstrates how White combines central pressure with development: d4 Nd7 Nbd2 exd4 h3 Bh5.

Development Alternatives: Nc3 and c3

Players preferring classical piece development frequently select Nc3, which accounts for 14.0% of encounters (4.5K recorded games) and an evaluation of +0.94. This move achieves a 53.8% score, often leading into Nc3 Nf6 h3 Bxf3 Qxf3 c6, where White secures the bishop pair. Alternatively, c3 is chosen in 13.2% of games (4.2K games, +0.85 evaluation) and scores 54.5%, preparing the central break while fortifying d4.

Prophylactic and Waiting Approaches

The modest rook lift Re1 appears in 7.6% of recorded games (2.4K games) with an evaluation of +0.81 and a 54.4% score. It prepares central expansion without rushing, as seen in the continuation Re1 Nd7 c3 g6 d4 Ngf6. While h3 immediately asks the question of Black's bishop, each of White's major alternatives retains an advantage due to Black's cramped pieces.