Morphy Defense, Tarrasch Variation

With 5. Nc3, White protects the e4-pawn by developing a piece instead of leaving it en prise with 5. O-O. The line is also called the Four Knights Variation, and it can occasionally arise from the Four Knights Game by transposition. The knight on c3 blocks White's c-pawn, so the usual Spanish plan of c3 and d4 is no longer available. Without that central tension, White has a harder time opening files for the rooks, and the bishop on a4 has no retreat to c2, which leaves it more exposed to exchange. White therefore tends to follow up with d3 and play for piece pressure, in particular the jump Nd5.

Black's most common reply by a wide margin is 5...b5, which settles the bishop's position at once. After 6. Bb3, Black usually chooses between 6...Be7 and 6...Bc5. A typical sequence is 5...b5 6. Bb3 Be7 7. d3. 5...Bc5 and 5...d6 are the other frequent choices. If White castles soon, the game often transposes into the Morphy Attack or other main lines. Engines regard the position as balanced, and White scores slightly better in online play.