By playing 6.d3 White steers clear of the Marshall Attack and any of the Anti-Marshall lines. White threatens 7.Bxc6 winning the e5-pawn leaving Black a choice of either 6...d6 or 6...b5. After 6...d6 the e5-pawn is firmly defended and Black threatens to trade off White's Ruy Lopez bishop with 7...b5 and 8...Na5. White normally continues with 7.c3 and after 8...0-0 White can choose between 9.Nbd2 or 9 Re1. Black can also play 6...b5 and after 7.Bb3 d6 (7...0-0 is a viable alternative) White has to deal with the threat of 8...Na5 by playing 8.a3 (8.c3 or 8 a4 are perfectly playable as well) and after 8...0-0 (the immediate 8...Na5 is also feasible) 9.Nc3 we have reached a modern tabiya of the Ruy Lopez. This position was first reached in a high-level encounter between Viswanathan Anand and Michael Adams, Grenke Chess Classic 2013. 6.d3 has gained wide popularity among the top players and has almost supplanted the Ruy Lopez main line with 6.Re1.