Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Bxc6

White chooses to trade off Black's knight for a bishop. This reduces Black's control of the centre, and alleviates the risk that White's bishop may become trapped on the queenside.

4...dxc6 is the main move. Taking back this way, though it takes a pawn away from the centre, opens lines for Black's queen and queen's bishop to enter the game. Black's e5 pawn is still defended tactically for now: Nxe5 may be met with ...Qd4!, forking the knight and e4 pawn. So, before White can win it they must defend e4: either 5. O-O intending Re1, or 5. Nc3. An alternative is 5. d4, attacking e5 and opening the centre.

4...bxc6?!, the Lutikov variation leaves White with a small advantage.

After 4...bxc6 White can win a pawn but Black gets compensation. 5. Nxe5!? Qe7! (pins the knight to the e4 pawn) 6. d4 (to defend knight) d6 7. Nxc6 Qxe4+ (Black recovers one pawn) 8. Qe2 Qxe2+ 9. Kxe2. White is up a pawn but, having lost castling rights, the position is not cut-and-dry.

More critical is to open the position and press their lead in development, e.g. 5. d4 exd4 6. Qxd4.

The Exchange Spanish was the main variation considered in 18th century analysis by the Modenese masters Ercole del Rio and Domenico Lorenzo Ponziani, leading them to prefer the 3. Bc4 over 3. Bb5. Later analysis favoured avoiding the exchange with 4. Ba4, which became the mainline.^[1]

Emanuel Lasker and later Bobby Fischer revived the Exchange in the 20th century.^[2]

For explanation of theory tables, see theory table and for notation, see algebraic notation..

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6

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Wikipedia has related information at Ruy Lopez, Exchange Variation

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.

• Nick de Firmian (1999). Modern Chess Openings (14 ed.). Random House. ISBN 0-8129-3084-3.