Exchange Variation, Normal Variation

Castling on move five, also known as the Barendregt Variation for Johan Barendregt, is the most common way to handle the Exchange Ruy Lopez. Unlike 5. d4, it opens nothing and instead revives the threat to e5. With White's king off the e-file, Nxe5 can no longer be answered by ...Qd4 and ...Qxe4, since Re1 then pins the queen. Bobby Fischer made the line a serious weapon in the 1960s, with well-known wins over Lajos Portisch and Svetozar Gligoric at the 1966 Havana Olympiad.

Black's most frequent reply is 5...Bd6, the King's Bishop Variation, which avoids the queen trade that 6. d4 can force elsewhere. The pin 5...Bg4 is nearly as common, and 5...Bg4 6. h3 h5 is the Alapin Gambit, where 7. hxg4 hxg4 opens the h-file against White's king. The Gligoric Variation, 5...f6, is the traditional main line; after 6. d4 exd4 7. Nxd4 c5 8. Nb3 Qxd1 9. Rxd1 the queens leave the board early. The rarer 5...Qd6, the Bronstein Variation, prepares queenside castling and pressure along the d-file. Engines consider the position balanced, with 5...Qf6 among their preferences, while White scores slightly better in practice.