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1.e4 e5 2.Nf3 Nc6 3.Bc4 Bc5 4.O-O

In recent years, the move 4.O-O has taken over from 4.d3 almost entirely -- in my database of TWIC games, if I look at 2750+ games from the last year, I see 4.0-0 70 times and 4.d3 only 5 times. They mostly seem to transpose into the same positions. This seems to be relatively recent and might be a factor behind the recent popularity of 3.Bc4 (related to the question What happened to the Giuoco Pianissimo? , I turned my comments there into this question).

What's the advantage of 4.O-O over 4.d3?

In case it helps, I seem to recall someone asking this elsewhere (maybe on Reddit?) and a helpful answer linked to some well known commentators explaining it (perhaps Svidler and Gustafsson?). I was at work and didn't watch the video, and I've forgotten where I saw it.

  • Probably either black recently managed to find an equalizing line after d3, or white managed to achieve something in some critical O-O-lines. (Svidler and Gustafsson usually commentate on chess24. If you can't find it there, maybe you can look up some recent prominent game in this variation, and look for the chess24 coverage of that game.)
    – TMM
    Oct 4, 2017 at 21:16
  • @TMM: exactly, the question is what that line is. I'm not all that sure it was Svidler and co. Oct 4, 2017 at 21:20
  • I think I saw this line somewhere recently as well, and seem to recall that it allowed for an improved Max Lange or Evans Gambit. If I can find the source, I will post it as an answer.
    – Herb
    Oct 4, 2017 at 21:41
  • This was the original line in the Evans (see chessgames.com/perl/chessgame?gid=1227672) and probably hasn't been looked at too seriously since around the 1860s. It's quite possible somebody has turned up something here or in a related line.
    – Ian Bush
    Oct 4, 2017 at 22:28
  • Remco@ You surprised me very much with your claim, but I have checked on Chessbase for 2700+ players in 2017, and the margin is something like 88-39. Mostly these games have the other move on the next turn, and are anyway the same games counted twice, so that may not mean much. None of the games enter immediate tactics and not one gets anywhere close to an Evans or a Max Lange, so I dont see any prospect of it being a tactical issue. I can't see it being anything but a coin toss. It still leaves the larger question, why a system despised for a century should suddenly become fashionable
    – Philip Roe
    Oct 5, 2017 at 3:31

3 Answers 3


According to a New in Chess Yearbook 124 article: "Recently, White has been playing this move order, intended to avoid lines that allow Black the possibility of a quick ...d7-d5(normally, this central break only works when White has played his pawn to c3). 4.c3 Nf6 5.d3 0-0 6.0-0 d5 is precisely what White is trying to avoid...


I see two reasons why to prefer castling over c3. First reason why I would go for 4.0-0 is that I would like to postpone playing c3 to make lines with d5 riskier. Imagine Marshall Ruy-Lopez, if the pawn was on c2, white would have very easy life, no weakness on d3, Nc3 possibility. And you can always play the c3 later if you like. The second thing may be desire to avoid playing c3 in early phase at all. White players tried to play a4 to create shelter for the bishop on a2, not minding exchange for opponent's bishop, avoiding classical Bb3-c2 plan.

  • 5
    The question was about the relative merits of 4.O-O and 4.d3. The move 4.c3 is seldom played unless White intends going into older lines with a subsequent d4. The issue raised was why a top player, intending to go into the modern Italian, would prefer the move order with 4.O-O.
    – Philip Roe
    Oct 5, 2017 at 15:02
  1. The move 0-0 leaves White's options open while developing. The other moves will determine White's plan.

  2. Castling will allow White to play a better version of the Giuoco Piano, but without the ..Bb4+.

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