Spanish Game / Ruy Lopez (Morphy Defence)

3...a6 "puts the question" to the white bishop: "You can take, or you can retreat, but you cannot stay here."

4. Bxc6 is the Exchange variation. White eliminates Black's knight, weakening e5. White can't take e5 straight away, however: after 4...dxc6 5. Nxe5? is met with 5...Qd4!, forking White's knight and e4 pawn. Although playable, the Exchange variation is not the main line.

4. Ba4 is the main line. As Carl Jaenisch determined in the 19th century,^[1], "the object of [3. Bb5] is not to double a Pawn for Black by taking his [Knight], but to confine the development of his right wing as long as possible." White preserves their bishop pair and the pressure on Black's knight.

Once White has played 4. Ba4, Black has the possibility of ending the threat on their knight by playing ...b5 at their leisure. In fact, White must take some care to not fall into the Noah's Ark Trap, in which Black traps White's bishop on the b3-square with an ...a6, ...b5, and ...c4 pawn advance on the queenside.

Although 3...a6 was known earlier, it became popular after it was played by 19th century chess prodigy Paul Morphy during his European tour. It is now by far the mainline.

For explanation of theory tables, see theory table and for notation, see algebraic notation.

1.e4 e5 2.Nf3 Nc6 3.Bb5 a6

When contributing to this Wikibook, please follow the Conventions for organization.

Wikipedia has related information at Ruy Lopez

• Kasparov, Garry, & Keene, Raymond 1989 Batsford chess openings 2. ISBN 0-8050-3409-9.