Closed Ruy Lopez question

I don't play 1.e4 e5 with either colour, but here's something I've wondered about. Perhaps someone here knows.

This is the main line of the Closed Ruy Lopez. It continues either 7...0-0 8.c3 d6, or 7...d6 8.c3 0-0, reaching the same position. Each must have its pros and cons, because both ways are popular.

The obvious advantage for black of playing 7...0-0 is that he "threatens" to play the Marshall Attack, 8.c3 d5. So much so that white's 8th move alternatives (8.a4, 8.h3, 8.d4, 8.d3) are called "anti-Marshall" systems. If these systems are inferior to the mainline 8.c3 d6, and black can entice white to play them, he has scored a tiny point, even if he never intended to play the Marshall.

But what is the advantage of playing 7...d6? Are the anti-Marshall moves (a4, h3, d4, d3) not as good against 7...d6?

In other words, what is the con of 7...0-0? Why doesn't everybody just castle?

Remko:  I have played Ruy-Lopez quite a bit (and still do) with black.

My take on your question is that 7...d6 used to be almost the default people played 10-20 years ago; the so-called Anti-Marshall moves you list were considered (and I think still are) inferior for white to the standard continuation 8.c3 O-O.

I am personally not aware of any direct drawback of choosing 7...O-O and then transposing to the mainline via 8.c3 d6.  The psychological trick (against those who know they might fear the Marshall attack) is that by playing 7...O-O you force them to consider if they would like to possibly play Marshall as white and those who don't might be tempted to avoid 8.c3 and therefore end up in variations that are, relatively speaking, more promising for black.

Maybe I'm missing something, but what you say just seems illogical :p I mean if, as you say, 7...0-0 "forces" white to play an anti-marshall move wouldn't that mean that white considers the main-line (i.e 8.c3) inferior? I mean from white's point of view he is always trying to make the best move, right? It can't be that both the Marshall Attack-variation and the Anti-Marshall-variation involve a weakening for white, because that would clearly mean that somewhere along the way to the 8th move white must have made a mistake.

Do you see what I'm trying to say? White can't have only poison apples to bite. As long as he has played sound opening moves there should always be another move that ensures at least equality methinks.

As far as I know, the Marshall Attack is believed to give black equality (but this can of course not be said for certain because the opening is too positional to be judged absolutely). So that should mean that white should want to avoid it. I read somewhere (wikipedia I think) that Kasparov plays 8.a4 just to avoid the Marshall, and that should mean that 8.a4 is not bad for white.

Please note though: These are just my thoughts and I'm neither high-rated nor an export on ruy lopez.

Whats interesting is that my database gives 8 a4  as scoring 60% against 7....0-0  and  61% against 7.... d6  so it appears that a4 is the best response to both moves !

Yep, I play 8.a4 against both moves and I always get a nice position.

If it's good enough for Kasparov, it's good enough for me.