Sicilian Defense: Four Knights Variation, Exchange Variation
The Four Knights Exchange is 6.Nxc6, where White trades the central knight for Black's c6 knight. Black chooses how to recapture: ...bxc6 strengthens the center, while ...dxc6 offers a queen trade and an even endgame.
- Moves
- 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Nf6 6.Nxc6
- ECO
- B45
- Engine
- +0.41 · a slight edge for White (Stockfish 17.1, depth 20)
- Played
- 785 games in our lichess sample
- White scores
- 49.0%
Key ideas for both sides
White
- After ...bxc6, push e5. The knight must go to d5, and Ne4 then eyes d6 and supports f4.
- After ...dxc6, take the queens and use Bf4 with long castling to pressure the d-file.
- Watch for loose pieces. If Black does not recapture, White is simply a knight up.
Black
- 6...bxc6 is natural: it adds a pawn to d5 support and opens the b-file.
- After e5 Nd5 Ne4, check with ...Qa5+ and retreat to b6 to pressure b2 and f2.
- 6...dxc6 leads to an endgame with the king on e8 or d8 and the pawn break ...e5 later.
- Never play 6...Qc7 here. It leaves the knight uncaptured and drops a full piece.
Plans and pawn structure
If Black recaptures with the b-pawn, the center is solid with c6, e6 and a chance of ...d5. White pushes e5 to gain space, uses Ne4 and Bd3, and tries to keep the d5 knight from becoming too strong. If Black recaptures with the d-pawn, the queens come off. White gets a small lead in development with Bf4 and O-O-O, but Black has no weaknesses and can play ...e5 and develop the c8 bishop to reach equality.
What the engine plays from here
Stockfish 17.1 at depth 20 rates the position +0.41: a slight edge for White. Its three top choices for Black:
- +0.41 6...dxc6 7.Qxd8+ Kxd8 8.Bf4 Ke8 9.O-O-O
- +0.45 6...bxc6 7.e5 Nd5 8.Ne4 Qa5+ 9.Bd2
- +4.42 6...Qc7 7.Nd4 a6 8.Bd3 b5 9.Qe2
Pawns, from White's side.
How it scores on lichess
785 rated lichess games reached this position; White scored 49.0%.
Light: White wins. Grey: draws. Dark: Black wins. About the sample.
How to play against it
With Black, recapture at once with a pawn. Choose ...bxc6 if you want a fighting middlegame and know the ...Qa5+ check that follows e5. Choose ...dxc6 if you are happy with a quiet queenless game and a king on e8. Do not make any other move first, or you are a piece down.
Questions
What are the moves of the Sicilian Defense: Four Knights Variation, Exchange Variation?
The Sicilian Defense: Four Knights Variation, Exchange Variation starts 1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Nf6 6.Nxc6. Its ECO code is B45.
Is the Sicilian Defense: Four Knights Variation, Exchange Variation good for White?
Stockfish 17.1 rates the position +0.41 at depth 20, which is a slight edge for White. In 785 lichess games from our sample, White scored 49.0%. A practical try for White players who like clear structures; Black should just recapture and know one of the two plans.
What is the main idea of the Sicilian Defense: Four Knights Variation, Exchange Variation?
White simplifies by trading on c6. Black picks between ...bxc6 for central control and counterplay, or ...dxc6 for an even queenless endgame.
What should Black play next?
The engine's first choice is dxc6, with bxc6 and Qc7 close behind. 6...dxc6 trades queens after Qxd8+ and gives a calm, balanced endgame.
Related lines
Updated October 2026. Sources and method.