Game six of the match, in which Caruana had Black, started with an unusual opening but quickly turned into an equal position in which both players did not seem to have much to play for.
However, Caruana gradually outplayed Carlsen from this seemingly harmless position and to avoid worse Carlsen eventually decided to give a piece for two pawns and put his hope on building a fortress in the endgame. A fortress which Caruana after more than five hours of play and with limited time on the clock could not crack.
However, the Norwegian supercomputer Sesse soon claimed that Black had a forced mate. But as strong as computers are they still struggle with fortresses and zugzwang. Endgame expert Karsten Müller analysed this complicated endgame from a human perspective and shows the way Black could have won.
