There are many openings with long variations, more or less forced, in their body of theory which are recognized as playable by both sides : Marshall Attack and Schliemann Defense in the Ruy Lopez, Botvinnik Variation in the Anti-Meran Semi-Slav, most systems of the KID, Traxler Counterattack in the Italian Game, English Attack in the Sicilian Najdorf, and many more...

But which opening variation has been analysed the deepest of all? Also, has one or more variations been analysed right to the endgame, and has it brought up a definite evaluation of the variation, perhaps of the opening too?

The opening line should ideally have either been analysed by recognized theoreticians in whichever material, or been used enough in practice by high level players (or computers) to support its validity. I'm not looking for whole games which used a very long opening line, unless the opening also ends up in a position with a proven outcome, like a solved endgame or perpetual check.

  • 2
    As long as it's not your main condition, 'analysed by recognized theoretitians' could be probably replaced with something more general. Are correspondence players good enough for that purpose? As there for example one English attack variation (23...Jf3) was analysed till tablebase draw. Are computer games good enough for your purpose? As in the poisoned pawn lines I saw lines heavily repeated till move 60 and in reality they were repeated probably much further, I only stopped being interested in them. Anyway good question.
    – hoacin
    Jul 10 '18 at 3:10
  • Lines that have been played in high level competition multiple times are good too, from whichever source (OTB, correspondence, computer, etc.), just there should be some evidence showing the opening sequence is not over, and players haven't begun improvising their moves. I'll edit my question. Also, both of your examples are indeed the sort of lines I was thinking about.
    – Umlin
    Jul 10 '18 at 9:32
  • 40+ moves for some lines of the Ruy Lopez, maybe the Marshall Attack variation?
    – Tony Ennis
    Jul 10 '18 at 11:22
  • 1
    Maybe the question should limit scope to published analysis. I have seen analysis in the Grünfeld Exchange beyond move 45.
    – Evargalo
    Jul 12 '18 at 16:11

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