Ruy Lopez 5.d4 exd4 6.Qxd4 and White is in . After 4...dxc6, the obvious 5.Nxe5 is weak, since 5...Qd4 6.Nf3 Qxe4+ 7.Qe2 Qxe2+ leaves White with no compensation for Black's bishop pair. There are two principal lines after 4.Bxc6 dxc6. In the late 19th and early 20th centuries, Lasker had great success with 5.d4 exd4 6.Qxd4 Qxd4 7.Nxd4. Since then, better defences for Black have been developed, and this line is considered to slightly favour Black. Jon Jacobs wrote in the July 2005 "Chess Life" (p. 21): "A database search (limited to games longer than 20 moves, both players FIDE 2300+) reveals
Sicilian Defence most part, other moves are the Closed Sicilian. Possible moves are 3.g3 and 3.f4 in general, also 3.Nge2, and less commonly 3.d3 and 3.Bc4. Some lines may transpose to the Open Sicilian, but there are many that do not. Also of some interest is 3.Bb5 to ...Nc6. A typical line is 2...Nc6 3.g3 ("ECO" code B24). Also 2...Nc6 3.f4 is the Closed Sicilian, Grand Prix Attack (part of B23). White can also keep their options open with 3.Nge2. Andrew Soltis has dubbed that the "Chameleon System", since White maintains the option of playing a Closed Sicilian with 4.g3 or transposing