Scandinavian Variation, Bogoljubow Variation, Vehre Variation

In the Vehre Variation Black declines to capture on e4 with the d-pawn and instead develops with 3...Nf6, putting a second piece on e4. This avoids the gambit lines that follow 3...dxe4 4. d5. Unlike 3...e6, it keeps Black out of a French structure. The cost is that the knight on f6 becomes a target. The engine gives White a clear advantage, and White's best replies all exploit that exposed knight or the pinned-down center.

By far the most common answer is 4. e5, chosen in well over half of games. It gains space with tempo, forces the knight off f6 and leaves White with a fixed pawn chain and a space advantage, while Black's c-pawn is still blocked by the knight on c6. The exchange 4. exd5 opens the position and lets White aim to harass whichever piece recaptures on d5. Less often, 4. f3 simply shores up e4 in the manner of the Blackmar-Diemer setups. In practice White scores somewhat better, most of all after 4. e5.