The much, but not long-awaited game between Magnus Carlsen and his latest challenger, Fabiano Caruana, took place in round 1, and it did not disappoint. At least it didn't disappoint fans looking for a hard-fought game; partisans of each player will have something to regret - but also to celebrate. Carlsen proved better in the middlegame, while Caruana demonstrated his defensive prowess and showed that Carlsen's vaunted technique isn't perfect.
The opening was unusual and full of little surprises: Caruana played 1.d4 and then chose a rather passive Anti-King's Indian/Anti-Gruenfeld with 4.e3. Carlsen turned the game into an oddball King's Indian, and outplayed his opponent in the non-standard middlegame that ensued. He eventually obtained a winning double-rook ending, but Caruana defended stoutly, and at a certain point in the second time control Carlsen was forced to find a difficult (but not impossible) winning move. He didn't manage to clear that last hurdle, and from there the draw wasn't too hard for Caruana to secure.
Four of the five games were drawn, and most of the drawn games had some adventures. Viswanathan Anand had White against Hou Yifan and played a risky, experimental opening, sacrificing a pawn and later an exchange. (Though by that time, he was a pawn up, so he had a pawn for the exchange.) Slightly reminiscent of the Karjakin-Caruana game from the Candidates - Caruana's only loss - Anand's compensation for the exchange was a brilliant bishop on d5. Hou's position was difficult, but she defended resourcefully and saved the game.
Arkadij Naiditsch's game with Maxime Vachier-Lagrave was a real barn-burner. Both players love extreme complications and handle them very well. This time around, Naiditsch handled them better for a good portion of the middlegame, but MVL managed to keep things wild and managed enough counterplay to draw.
Georg Meier's game with Levon Aronian was the dullest game of the round; not exactly a shock given Meier's 5.Re1 against the Berlin. There are exceptions in Meier's repertoire, but for the most part he plays risk-averse chess, trying to obtain small advantages and then grind away with his excellent technical skills. It's unlikely to prove successful against the top players in the field, but then again he won't lose to them in such situations, either.
Finally, the one decisive game was a keeper, a minor brilliancy sure to make the rounds. The first 19 moves of Matthias Bluebaum-Nikita Vitiugov looked likely to result in a draw, but then Bluebaum fell into a very deep trap. Vitiugov's 21...Rxf2! was the start of a combination running a dozen or so moves in the main line, requiring a number of precise, subtle, beautiful moves to work. I've annotated this game, along with Caruana-Carlsen, and all five games can be replayed here.
The round 2 pairings are Carlsen - Hou Yifan, Vachier-Lagrave - Anand, Aronian - Naiditsch, Vitiugov - Meier, and Caruana - Bluebaum. The higher-rated player has the white pieces in every game, and it's a significant rating difference in all of them but MVL-Anand.