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
Salo Flohr players ever, and proved virtually invincible at the Olympiads of the 1930s. His tournament record was impressive, with his tactical skill and excellent endgame technique securing him many famous victories. FIDE awarded him the International Grandmaster title on its inaugural list in 1950. He made a number of important contributions to opening theory: a 'Flohr variation' can be found in no fewer than six major openings, including the Caro–Kann Defence, the Ruy Lopez, the English Opening, and the Grünfeld Defence. The Flohr–Zaitsev Variation of the Closed Ruy Lopez (1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.0-0 Be7 6.Re1 b5