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Chess Opening Theory/1. e4/1...e5/2. Nf3/2...d6/3. d4/3...Nd7/4. Bc4/4...Be7/5. dxe5/5...dxe5/6. Qd5
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Hanham variation C41 Philidor defence → Hanham variation → 5...dxe5
6. Qd5
White threatens Qxf7#. Black can defend against the threat only by conceding a minor piece:
6...Nh6 defends the f7 square, but after 7. Bxh6 the threat is renewed. Black can defend the pawn with their rook (7...O-O or 7...Rf8) but is not in time to recapture the bishop.
6...Bb4+ forestalls the mating attack while freeing the e7 square, from where Black's queen can defend f7. After 7. c3 Qe7 mate is prevented but Black's bishop is hanging.
Theory table
References
See also