Central Variation, McDonnell Defense

The McDonnell Defense answers White's broad center with an immediate counterblow, 3...e5, which challenges d4 and opens the diagonal of the f8-bishop. It is the most common and most ambitious reply to 3. e4. The name comes from Alexander McDonnell, who met it in an 1834 game against Louis de La Bourdonnais. In that game White chose 4. d5, still the most frequent move on Lichess, although it overextends the center and invites undermining with ...c6 and ...Bb4.

The principled move is 4. Nf3, which hits e5 and protects d4. A typical continuation is 4...exd4 5. Bxc4 Nc6 6. O-O Be6, with White trading the extra center pawn for rapid development. The natural-looking alternatives misfire. After 4. Bxc4, the Somov Gambit, Black plays 4...Qxd4 5. Qxd4 exd4 6. Nf3 c5 and keeps a stable pawn center. 4. dxe5 Qxd1+ forces Kxd1, leaving the material level but costing White the right to castle. The engine rates the position as roughly balanced, and White scores somewhat better than Black in online play.