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 a significant advantage against it in the 18th game. It is solid but slightly passive. Confusingly 9...Nd7 is also called the Chigorin Variation so there are two variations of the Ruy Lopez with that name, but 9...Na5 is the move more commonly associated with Chigorin. This defense is also known as the Keres Variation, after Paul Keres. The Kholmov Variation, 9...Be6, was popular in the 1980s but is now rarely played. The main line runs 10.d4 Bxb3 11.axb3 (11.Qxb3 is another option) exd4 12.cxd4 d5 13.e5 Ne4 14.Nc3 f5 15.exf6 Bxf6 16.Nxe4 dxe4 17.Rxe4 Qd5 18.Rg4, when it has been