1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Bxc6 dxc6
The most frequently played move against the Spanish bishop development after b5 is the direct questioning of the bishop with 3...a6. White then has two basic continuations at their disposal: the retreat 4.Ba4, which initially maintains the pressure against the Nc6, and 4.Bxc6 - the exchange variation. However, the idea of 4.Bxc6 is by no means to win the e5-pawn, because after 4...dxc6 5.Nxe5 the double attack 5...Qd4 would immediately recapture the material advantage. The much deeper strategic idea behind this line, which was often chosen by the world champions Bobby Fischer (1943-2008) and Emanuel Lasker (1868-1941), among others, is that White wants to exchange their d-pawn for the black e-pawn in the next few moves. White then obtains a 4:3 pawn majority on the kingside, while Black's majority on the queenside is devalued by the double pawn and cannot so easily produce a passed pawn. The ideal scenario for White is a pure pawn ending, which under normal circumstances is won without too much difficulty. Black will do everything in their power to prevent this dream. Since his position is very compact and he is also in possession of the bishop pair, he should normally be able to equalise. A typical variation would be 5.0-0 f6 6.d4 exd4 7.Nxd4 c5 8.Ne2 Qxd1 9.Rxd1 Bd7:
The black king will castle on the queenside, with ...Bc6 and ...Re8 the e-pawn is put under pressure. White can develop with Nbc3 and Be3 and then double the rooks on the d-file. However, after 5.0-0 Black has quite a wide choice of moves, but on the other hand this does little to change the overall character of the position.
5...f6 is the most frequently played move, 5...Qd6, 5...Qf6, 5...Bd6 and even 5...Ne7 are also possible. More tactical than the other lines is 5...Bg4, because 6.h3 can be followed by 6... h5 can follow, whereupon capturing the bishop 7.hxg4? is forbidden because of 7...hxg4 with the opening of the h-file and the threat of ...Qh4.
With the exchange variation White first decides where to go. Although Black has a choice of several good replies, it is not easy for them to play for a win. Those who like to plan their game with a crystal-clear strategy that extends into the endgame are recommended to follow the example of the world champions Lasker and Fischer.