It seems as Nakamura caught his opponent into a three-fold repetition machine.
1. e2e4  1... e7e6 The starting position reveals a relative queenside weakness. Especially vulnerable is the a7-pawn and an important detail is that neither of the sides can defend it even after it castles long. 2. f2f4  2... d7d5  3. h1g3  3... a8b6  4. a1b3  4... d5e4 Nakamura wants to win a tempo to develop his light-squared bishop, while fighting for the center. The only drawback of the move is that it pushes the white knight where it wants to be. 5. g3e4  5... f7f5  6. e4c3  6... g7g5 The continuation of the strategy. 7. f4g5  7... e8h5  8. f1e2 Automatic reply by Fedoseev. 8... h5e2  9. c3e2  9... g8g5  10. e1g3  10... h8g6 Not just developing, but looking for a quick closure of the diagonal. 11. e2d4 Back to the enemy queenside (and king $1) This is already a double attack. 11... d8e8  12. d4b5 White wins a pawn and there should not be enough compensation. 12... f5f4  13. b5a7  13... c8d8  14. g3f2  14... b6d7 Cutting the knight's way back. 15. d1e1 But Fedoseev does not intend to move backwards with the knight. He rather prefers to use it in the attack instead. 15... b8a8  16. e1e4  16... c7c5  17. e4a4 The most obvious, and a good continuation. 17... d7b6  18. a4a5 