Chess Opening Theory/1. e4/1...e5/2. d4/2...d6

a b c d e f g h
8a8 black rookb8 black knightc8 black bishopd8 black queene8 black kingf8 black bishopg8 black knighth8 black rook8
7a7 black pawnb7 black pawnc7 black pawnd7 black kinge7 black kingf7 black pawng7 black pawnh7 black pawn7
6a6 black kingb6 black kingc6 black kingd6 black pawne6 black kingf6 black kingg6 black kingh6 black king6
5a5 black kingb5 black kingc5 black kingd5 black kinge5 black pawnf5 black kingg5 black kingh5 black king5
4a4 black kingb4 black kingc4 black kingd4 white pawne4 white pawnf4 black kingg4 black kingh4 black king4
3a3 black kingb3 black kingc3 black kingd3 black kinge3 black kingf3 black kingg3 black kingh3 black king3
2a2 white pawnb2 white pawnc2 white pawnd2 black kinge2 black kingf2 white pawng2 white pawnh2 white pawn2
1a1 white rookb1 white knightc1 white bishopd1 white queene1 white kingf1 white bishopg1 white knighth1 white rook1
a b c d e f g h
Position in Forsyth-Edwards Notation (FEN)
Moves: 1. e4 e5 2. d4 d6

2...d6

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This is an inferior way to enter a Philidor. While white's best move is still Nf3 transposing into the Philidor, it gives them the additional option of immediately entering an endgame with dxe5 dxe5 Qxd8+ Kxd8 Bc4, though practically black hasn't had trouble defending it. Black would lose the right to castle, and White would have a lead in development. According to chess365, after 5.Bc4, white wins 42.1%, 32.5% end in a draw, and 25.1% end in a black victory. White can also enter a Chekhover-like position via Nc3 exd4 Qxd4 with the intention to respond to Nc6 with the Bb5 pin or drawing the queen back to d3 or e3 and simply enjoying their space advantage.

As such, it is considered strictly inferior to the Philidor move order, because white's sideline alternatives after e4 e5 Nf3 d6 are much less aggressive.

Theory table

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3 4 5
dxe5

dxe5

Qxd8+

Kxd8

Bc4 +/=
Nf3 =