Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6/4. Bxc6/4...dxc6/5. O-O/5...f6

Black defends their hanging e5 pawn.

6. d4 is the main move. Black is behind in development and at best still three moves from castling, so it's incumbent on White to strike fast and open the centre. Black wishes to avoid dxe4 fxe4 Nxe4, so the main continuation is 6...exd4 7. Nxd4. After 7...c5 8. Nb3 Qxd1 9. Rxd1 this goes into an endgame. An alternative is 6...Bg4 to pin the knight. If 7. dxe4 there may still be a queen trade, but otherwise White can keep a centre with 7. c3.

An early appearance of this line was in the 1904 German chess congress, which continued 6. d6.^[1]

It became popular in the 1960s, played by Spassky and others. Bobby Fischer (1943―2008) faced this line from Svetozar Gligorić (1923―2012) in 1966. The game continued in the 6. d4 Bg4 7. c3 line.^[2] He faced the 6. d4 exd4 7. Nxd4 line in his 1992 grudge match with Boris Spassky (1937―2025).^[3]

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 dxc6 5. O-O f6

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