Three Knights, Vienna Variation

The Vienna Variation arises when Black, after 4. Nf3 has produced the Three Knights, captures on c4 at once instead of maintaining the d5 point. Black does not aim to keep the extra pawn. The idea is to use the time White spends regaining it for active piece play, typically ...Bb4 to pin the c3-knight and ...c5 to strike at d4. The most common reply is 5. e4, occupying the center, and the main line continues 5...Bb4 6. Bg5. White gets a broad center and free development but accepts long-term weaknesses in the pawn structure. The same complex is often reached from the Ragozin via 4...Bb4 5. Bg5 dxc4, with a typical continuation 6. e4 c5 7. Bxc4 cxd4 8. Nxd4. 5. Bg5 is the second most popular choice. 5. e3, the Quiet Variation, simply prepares to recapture with the bishop, and the engine also considers 5. Qa4+.

The engine rates the position as roughly balanced, while White scores somewhat better in practice. The variation has a long top-level pedigree, with Fine–Euwe, AVRO 1938, an early example.