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 so it is difficult for White to exploit his structural superiority without opening the game for Black's bishops; all four of the games in the Kasparov–Kramnik match in which this line was employed ended in draws. An alternative for Black, though seldom seen since the 1890s, is 6...bxc6 7.dxe5 Nb7, although White keeps an advantage despite Black's two bishops, as it is difficult for him to gain active counterplay. White's move 4.Nc3 transposes to the Four Knights Game, Spanish Variation. Another possible try for White is 4.d3. This is "Steinitz's move, with which he scored many spectacular successes during his