Fischer Defense

With 3...d6 Black delays ...g5 until White has committed. The pawn controls e5, so after a later h4 and ...g4 the f3-knight cannot use that square. The move also opens the c8-bishop's diagonal and gives the king room on d7, at the price of hemming in the f8-bishop. Bobby Fischer popularized it after losing to Boris Spassky in the Kieseritzky in 1960, calling it a high-class waiting move in his analysis claiming a refutation of the gambit. Engines give Black a slight edge, though White scores better in online games.

The two main replies are almost equally common. After 4. Bc4, Black often plays 4...h6 5. d4 g5 6. O-O Bg7, reaching the Hanstein Gambit; 4...Be6 is a reasonable alternative, and 4...g5 is met by 5. h4. After 4. d4 g5 5. h4 g4, White cannot use e5, 6. Ng5 runs into 6...f6, and 6. Nfd2 shuts in the c1-bishop, leaving 6. Ng1. Neither side then has a developed piece, but White retains attacking prospects and central play. The Spanish Variation, 4. d4 Nf6 5. Bd3, and the Schulder Gambit, 4. b4, are less common.