Three Knights Variation, Hungarian Attack

The Hungarian Attack, 5. Bf4, places White's dark-squared bishop on the h2–b8 diagonal before the e-pawn moves. A later e3 then leaves the bishop outside the pawn chain, which is the main difference from the Burille Variation, where 5. e3 comes first. The bishop presses on c7 and the queenside dark squares, and White keeps open the choice between the restrained 6. e3 and the sharper 6. Qb3, which pressures d5 and c4. Black usually castles. After 5...O-O 6. e3, the Hungarian Variation, Black typically counters in the center with ...c5 or ...dxc4. 5...c6 bolsters d5 in Slav fashion, and 5...c5 attacks d4 at once.

The engine considers the position level, and Lichess results are close to even. The line is best known from Donald Byrne versus Bobby Fischer, New York 1956, the "Game of the Century". That game reached the position by transposition through 1. Nf3 Nf6 2. c4 g6 3. Nc3 Bg7 4. d4 O-O 5. Bf4 d5 and continued 6. Qb3 dxc4 7. Qxc4 c6 8. e4. Black's subsequent sacrificial play in that game made the line famous.