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 Neo-Steinitz Defence) ("ECO" C71–C76), Black interpolates 3...a6 4.Ba4 before playing 4...d6, which was frequently played by Alekhine, José Raúl Capablanca and Paul Keres. The possibility of breaking the pin with a timely ...b5 gives Black more latitude than in the Old Steinitz Defence; in particular, in the Old Steinitz, White can practically force Black to give up his strongpoint at e5, but in the Modern Steinitz, Black is able to maintain his . Most plausible White moves are playable here, including 5.c3, 5.c4, 5.Bxc6, 5.d4, and 5.0-0. The sharp Siesta Variation arises after 5.c3 f5, while a manoeuvring game results