comment: Threatening Rb3 and mate.
context: 1. e2e4 Once again, advancing the king's pawn is the best move. 1.d4 or 1.g3 is also acceptable, but I think the move played is the most accurate. 1... e7e5  2. g2g3 Bringing the bishop into the game. 2... d7d6  3. d2d4  3... e5d4  4. d1d4 There's no knight going to c6 (as would be typical for a queen on d4 in a regular position), but the bishop on h8 is the danger. 4... g8e7  5. f2f4  5... g7g6  6. d4d3  6... f7f5 This allows White to exploit the pin, as Black's queen is unprotected on d8. 7. c1d2 Missing the chance. 7... e8f6  8. e4f5  8... c8f5  9. d3b3  9... f5e4  10. g1f3  10... d8d7  11. e1d3  11... b8a8 A curious situation: White (surprisingly) can choose which side to castle to. 12. b1a1 The right way. 12... d8e8 Black has several good alternatives to this move. 13. d2c3  13... e4d5  14. b3a3  14... e7c6 After this move, Fedoseev finds a very interesting tactical idea. 15. c3f6 Strategically, it's undesirable to exchange the bishop for the knight, but White has a concrete idea in mind. 15... h8f6  16. f3e5 This is the point. White will get Black's light-squared bishop, leaving his own light-squared bishop unopposed on the a8-h1 diagonal. 16... f6e5  17. d3e5  17... d6e5 Making things even worse. 18. d1d5  18... d7e7  19. d5c5 The bishop on h1 is too strong. 19... e5f4  20. h1c6  20... b7c6  21. a3a6  21... c8b8 