Euwe Defense, Duthilleul Gambit

The Duthilleul Gambit, 6. Bd3, is White's direct response to the Euwe Defense. Rather than first pinning the f6-knight with 6. Bg5, White places the bishop on the b1-h7 diagonal at once, prepares quick kingside castling and keeps the half-open f-file in reserve for the rooks. The pawn deficit remains, so White's compensation rests on development and attacking prospects against a black king that will usually castle short. In online games it is the most frequent answer to 5...e6, and White scores very well with it in practice.

Black's two main replies are about equally common. 6...Bb4 pins the c3-knight, but in practice it has gone badly for Black. 6...Be7 is the quieter developing move and gives Black noticeably better results. 6...Nc6 is also played. The engine's first choice is 6...c5, striking at d4 straight away before White can complete development, and it judges the position slightly better for Black, even though White wins most games played from here.