Ruy Lopez: Why is d5 (marshall attack) only played after 8. c3

My opponent played 8. a3 in the ruy lopez and i still played 8... d5 because i am experimenting with the Marshall and I tought that that was, what i was playing :-)

I got a good game, and i won. But when analyzing, I noticed that this move is never played in the masters database, alltough the eval of the position is still pretty good for black and in the Lichess database it is played a lot and with good results for black.

Also a4 or d3 are even named 'anti-marshall'. I tried browsing a few lines, but i fail to see why d4 only works after white has played c3. Any help?

I am not trying to memorize lines, i am trying to understand what I am doing. For me: marshall means deflecting and removing the defenders of whites kingside and making him lose considerable tempo

After a4 you cant play d5 because b pawb hangs

I think the point is that c3 is a "slow" move that prepares d4, which is a pretty good idea if the position stays closed and both players just keep building up gradually. If black goes into the Marshall instead, playing c3 to prepare d4 becomes redundant (since there's no pawn on e5 and white could just have played d4 anyway) and c3 is just a wasted move that doesn't slow down black's attack and actively hinders the development of the queen's side, both of which are now fairly urgent. If white gets in a useful developing move (d6) or defensive move instead then it takes a bit of the sting out of the attack and make the gambit a bit less good. This probably doesn't make much difference to the average club player but is presumably quite relevant at GM level.

a4 is a bit of a different case - it looks like d5 just fails tactically to axb5 ideas, which hit the c6 knight and generally leaves black in a bit of a mess.

@JodyUmmels said in #1:
> My opponent played 8. a3 in the ruy lopez and i still played 8... d5 because i am experimenting with the Marshall and I tought that that was, what i was playing :-)
>
> I got a good game, and i won. But when analyzing, I noticed that this move is never played in the masters database, alltough the eval of the position is still pretty good for black and in the Lichess database it is played a lot and with good results for black.

In the h3/a3 anti-Marshall white retains good flexibility. If you play ...d5 and sacrifice a pawn, white can safely capture on e5 and you'll have insufficient counterplay to justify a full pawn.

@JodyUmmels said in #1:
> Also a4 or d3 are even named 'anti-marshall'. I tried browsing a few lines, but i fail to see why d4 only works after white has played c3. Any help?

I assume you mean ...d5, not d4. There are several differences:
* White's h3 pre-empts black's Bd6/Qh4 idea. No tempi for black here.
* White hasn't committed the pawn to c3. If black plays ...d5 white can quickly develop with Nc3 instead of the usual d4-Nd2.
* White plays d3 early in some of the anti-Marshalls. Again, if black gambits a pawn with ...d5 white is more prepared to rapidly develop pieces.
* Against the a4 anti-Marshall you won't usually have time to play ...d5 because your queenside is being attacked.

As you point out, the Marshall relies on generating initiative against the white kingside by deflecting or trading white's defenders off. Compare white's normal positions, where there aren't a lot of kingside defenders, to those that occur directly after you play ...d5 in an anti-Marshall: white can readily bring more pieces to the aid of the king.

The Marshall defence is one of the most interesting positions in chess, and a great opening to learn. If you're planning on including it in your permanent repertoire, just be forewarned that you're going to face a lot of anti-Marshalls. A lot. Exactly 1/3 of my games on lichess that reach that point are anti-Marshalls.

My $0.02? In general, I think most of the lines in the Closed Ruy are more interesting than anti-Marshalls, and although I love the Marshall, I hung it up eventually because I was less interested in having my fun once in awhile than I was in choosing consistently interesting positions as black. Even if I never get to play ...Qh4 with tempo any more :(

It is not only played after c3 although there is some reasons why it's good after this move.
- If white plays d4 the pawn up is stable but the piece activation is lacking, thanks to c3 that stucks the knight.
- If white plays d3 it has a better piece play thanks to the Re4 resource but it gives back the pawn, thanks to c3 that weakens d3.

But d5 can still be efficient to expose some slow weakening moves, i.e 8.h3 Bb7 9.d3 d5 !? is fine, probably the main reason why 8.h3 isn't that popular nowadays.
Seems fine against 8.a3 ?! as well I guess. Little sense to push that pawn by only 1 though.

Against more active moves like 8.a4 9.d3 or direct 8.d3 it shouldn't work since these are usefull enough moves against the marshall setup. If you still go for it and compare it to main Marshall white can claim being a tempo up with lower weaknesses for free.

thank you all.
This helps a lot!

MAgnus carlsen line against nepo might of be interest to you specifically game 1

@Ben10Tenyson said in #2:
> After a4 you cant play d5 because b pawb hangs
It is pawn not pawb

yeah my bad i am pretty bad at chess.