Ruy Lopez 3...a6 & 6...Bc5 setup - a4 vs c3+d4 idea for White? Here's the position after 1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 6.Bb3 Bc5



      [StartPly "12"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 6.Bb3 Bc5




There are 2 main continuations for White: 7.c3 (the most obvious imho) and 7.a4. Actually there's also the modestly looking 7.d3 which is good, no doubt, but I'm not interested in the d3 system at the moment)

What are the pros and cons of the the both moves/lines?

And what does White really achieve (or try to achieve) by attacking the pawn on b5? I understand it cannot be recaptured by the a-pawn, so Black would normally defend it with his rook or go Bb7. Second, I'd also like to understand why 7...b4 is bad from positional point of view.

Also, sometimes White precedes a4 with c3. So, instead of playing a4 right away he waits for 7...d6 and only then plays 8.a4 (again instead of the obvious to me 8.d4). What is the idea here?



      [StartPly "15"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 6.Bb3 Bc5 7.c3 d6 8.a4




Thank you.
After the logical 7.c3 d6 8.d4, black should play 8....Bb6, with the idea 0-0, Re8, Bb7/g4, building up pressure against white's center. Also after 8.a4 Bg4!, pinning the knight and protecting the rook on a8, black should be fine.

Therefore, the main line is 7.a4, bringing the rook into play with an extra tempo. After 7....b4, white obtains the advantage by 8.Nxe5! Nxe5 9.d4 Bxd4 10.Qxd4, attacking the pawn on b4. Note the difference with 7.Nxe5, where black is fine after 7....Nxe5 8.d4 Bxd4 9.Qxd4 d6.

Instead of 7....b4, the main line is 7....Rb8 and the game often continues with 8.c3 d6 9.d4 Bb6. This position can also be reached by 7.c3 d6 8.d4 Bb6 9.a4 Rb8. However, this move order unnecessarily gives black the extra option of 9....Bg4.

Recently, during the international tournament of the Isle Of Man, two top-level games were played that are important for the current theoretical status of the Ruy Lopez Arkhangelsk.

In the game Fabiano Caruana - Gawain Jones, black followed the recommendation given in a video series by Peter Svidler. However, during his home preparation, white found the refutation at move 23(!) and won the game (see reports on Chess.com and ChessBase.com).

Remarkably, the very next round, Magnus Carlsen repeated the same opening against Caruana. He deviated at move 14, but again Caruana had prepared a strong novelty. Nevertheless, Carlsen won (see reports on Chess.com and ChessBase.com).

Edit: In both games, Caruana chose the move order 7.c3 d6 8.a4, allowing 8....Bg4. Although this probably has a reason, I have no idea why this move order would be more precise.



      [StartPly "12"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nc6 3.Bb5 a6 4.Ba4 Nf6 5.O-O b5 6.Bb3 Bc5 7.a4 (7.Nxe5 Nxe5 8.d4 Bxd4 9.Qxd4 d6)(7.c3 d6 8.d4 (8.a4 Bg4) Bb6 9.a4 Bg4) Rb8 (7...b4 8.Nxe5 Nxe5 9.d4 Bxd4 10.Qxd4) 8.c3 d6 9.d4 Bb6