Ruy Lopez that after the common retreat 4.Ba4, Black will have the possibility of breaking a future pin on his by playing ...b5. White must take some care not to fall into the Ruy Lopez, Noah's Ark Trap, in which Black traps White's on the b3-square with a ...a6, ...b5, and ...c4 pawn advance on the . Ercole del Rio, in his 1750 treatise "Sopra il giuoco degli Scacchi, Osservazioni pratiche dell'anonimo Modenese" (On the game of Chess, practical Observations by an anonymous Modenese), was the first author to mention 3...a6. However, the move became popular after it was played by Paul
Ruy Lopez move there are many reasonable alternatives, and most have been deeply explored. It is convenient to divide the possibilities into two groups based on whether or not Black responds with (3...a6), which is named the Morphy Defence after Paul Morphy, although he was not the originator of the line. The variations with Black moves other than 3...a6 are older and generally simpler, but the Morphy Defence lines are more commonly played. By far the most commonly played third move for Black is the Morphy Defence, 3...a6, which "puts the question" to the white bishop. The main point of 3...a6 is