Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...a6

Morphy defence C70 Spanish game 4. Ba4 · Main Line 4. Bxc6 · Exchange Variation 3...a6 · 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,Carl Jaenisch 1848 Major Jaenisch On Ruy Lopez' Knight's Game Chess Player's Chronicle 9 216-21,248-53,274-79 https://www.google.ch/books/edition/The_chess_player_s_chronicle/ja5AAAAAcAAJ?hl=en&gbpv=1&pg=PA216 9 June 2025, "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. History Although 3...a6 had been 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 main line. Theory table 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4 5 Exchange Variation Bxc6dxc6 O-Of6 = Norwegian Defence Ba4b5 Bb3Na5 = Classical Defence Deferred ...Bc5 O-ONf6 += Steinitz Defence Deferred ...d6 O-OBg4 += Arkhangelsk Defence ...Nf6 O-Ob5 ∞ Møller Defence ...... ...Bc5 += Russian Defence ...... ...d6 += Open Defence ...... ...Nxe4 = Main Line/Closed Defence ...... ...Be7 = References See also Ruy Lopez fi:Shakkiaapinen/Peli/1. e4/1...e5/2. Rf3/2...Rc6/3. Lb5/3...a6