Nimzowitsch Variation

The Nimzowitsch Variation answers 3. d4 by leaving e5 en prise and hitting the e4-pawn instead. Aron Nimzowitsch favored it to sidestep the awkward 3...Nd7 4. Bc4. If White defends with 4. Nc3, the usual choice in tournament play, then 4...Nbd7 reaches the Hanham strongpoint structure (the Lion Variation), while 4...exd4 transposes to the Exchange Variation. The drawback is 4. dxe5, by far the most frequent reply in the database. After 4...Nxe4, the tame 5. exd6 Bxd6 equalizes, so White prefers the Rellstab Variation 5. Qd5. After 5...Nc5 6. Bg5 Be7 7. exd6 Qxd6 8. Nc3 Qxd5 9. Nxd5 Bd6 the queens are gone and White keeps a small edge in the open center thanks to Black's lagging development. The Sokolsky Variation 5. Nbd2 is a quieter way to challenge the e4-knight.

The Klein Variation 4. Bc4 invites 4...Nxe4 5. dxe5, eyeing f7; 5...c6 is considered the most reliable reply. The Locock Variation 4. Ng5 is dubious but contains traps. Engines give White a slight advantage.