Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nf6/3. Nxe5/3...Nxe4/4. Qe2/4...Qe7/5. Qxe4

=Petrov's Defence, Damiano Variation=

5. Qxe4
At this point, black can no longer afford to maintain symmetry (5...Qxe5 6. Qxe5+ and black is down a queen for no compensation). Instead, 5...d6 offers a pawn for some compensation. While it is unclear if it is objectively enough, it offers non-trivial practical chances. In fact, in the best response by white this pawn is given back since white cannot hold onto it without getting a worse position.

The follow up is 5...d6 6. d4 dxe5 7. dxe5 Nc6 8. Nc3 Qxe5 9. Qxe5 Nxe5

Another popular try by white is 8. Bb5 Bd7, but that line also gives the pawn back in the end with 9. Nc3 0-0-0 10. 0-0 Nxe5 11. Bxd7 Nxd7

(If white plays 9. 0-0 0-0-0 10. Re1 attempting to hold onto the pawn, black can capture the pawn anyway due to 10...Nxe5 11. Bxd7+ Rxd7 12. Qxe5?? Qxe5 13. Rxe5?? Rd1+ 14. Re1 Rxe1#)

A popular trap for black arises after 8. Bf4 g5 9. Bg3?? f5! where the white dark squared bishop will be trapped after the queen moves away from the attack and black plays 10...f6!

While this position almost only occurs among beginners, the pawn sacrifice can offer interesting play up to fairly high levels, especially against greedy players who think that the pawn can be held onto without risk.

Theory table
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1. e4 e5 2. Nf3 Nf6 3. Nxe5 Nxe4 4. Qe2 Qe7 5. Qxe4