Chess Opening Theory/1. e4/1...e5/2. Nc3/2...Nf6/3. f4/3...d5/4. fxe5/4...Nxe4/5. d3

=Vienna Game= As no good square is available to retreat, Black should exchange the knight : /5...Nxc3/.

The other options include two ways of launching aggressive attacks against White :
 * /5...Bb4/
 * 5...Qh4+

Theory table
.

1. e4 e5 2. Nc3 Nf6 3. f4 d5 4. fxe5 Nxe4 5. d3