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

=Petrov's Defence, Damiano Variation=

4. Qe2
White threatens the black knight, but if the black knight moves immediately, black will lose material. For this reason, 4...Qe7 is the best reply.

This position is most common among beginners, but when played by strong players the line is an interesting pawn sacrifice (see the modest +/= evaluation given to the main line, 4.Qe2 Qe7 5.Qxe4 d6, in the theory table below).

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