Budapest Gambit Accepted, Main Line, Adler Variation

With 4. Nf3 White defends e5 but does not try to keep the pawn indefinitely. The plan is to bring every piece to an active post, with the queen's knight heading for d5 and the queen's bishop for the long diagonal. The name comes from Adler versus Maróczy, Budapest 1896. The main reply, 4...Bc5, makes White play 5. e3, and Black usually regains the pawn, for example with 5...Nc6 6. Be2 O-O 7. O-O Re8 8. Nc3 Ngxe5 9. Nxe5 Nxe5. In that position White has two main plans. The older one is 10. b3 with Bb2, central pressure through Qd5 and Ne4, and an eventual c4-c5, which Black meets with ...a5 and the rook lift ...Ra6-h6. The other is 10. Kh1 followed by f4, Bd3 and Qh5, an attacking plan introduced by Spassky against Illescas at Linares 1990. Against it Black aims at the weak e3-pawn. A recurring question for White is whether to insert a2-a3. The alternative 4...Nc6 postpones the decision about the dark-squared bishop and lets White transpose to the Rubinstein with 5. Bf4. Engines give White a slight edge, but the results are level.