A double-edged pawn advance.
1. e2e4  1... e7e5  2. g1f3  2... g8f6 The Petroff Defense seems too boring for a player with as fun a style as Van Foreest, but he has new ideas to play it more dynamically. The truth is that the old prejudices that players of my generation have against the Petroff, the Berlin, the London System, must be put aside, as the newer generation shows nearly every day. Well, maybe not in the case of the Berlin. 3. f3e5  3... d7d6  4. e5f3  4... f6e4  5. d2d4  5... d6d5  6. f1d3  6... c8e6 I have to admit I've never seen this move before. In fact, it's only been played a handful of times, at least compared to the vast amount of theory that goes into the Petroff Defense. This move is only Black's tenth most popular choice. Van Foreest once again lives up to his fame as an explorer of little-known paths. 7. e1g1  7... f7f5 It's important to note that the theory in this position is composed almost exclusively of correspondence games. Of course, the pawn advance creates some weaknesses in Black's camp, and pawn structure will be the main strategic theme of this game. But the knight is reinforced in his position on e4 and he has no intention of leaving, not even if attacked. 8. d1e2 Played after a long thought, indicating that even Caruana can be surprised in the opening. 8... f8e7  9. f3e5 A natural move for a human, but a theoretical novelty, which in this case implicitly means that it is not the most recommended move by the machine. 9... b8d7 The Dutch GM was clearly still in his preparation, judging by the speed with which he executed this move. 10. e5d7  10... d8d7  11. f2f3  11... e8g8 It's always a joy when we don't have to retreat a piece attacked by a pawn. 12. c1f4  12... e7f6  13. c2c3 Finally White threatens to take the knight for real.