Note that if White castles Black can play … ne5 (hitting the queen) followed by … nf3 check and … qh3 checkmate. A lot of weak white squares on the White kingside.
Fabiano plays 25. Nd5 (what else is there?) to which Black replies 25. … e4. The scorned g6 knight defends against c7 … Bx c7 Ne7 check – forking the king and queen. The black knight may be able to go to e5 forking the queen and pawn. The first notes of the famed Puccini tenor aria “Nessun dorma” (= no sleep or not sleeping) from the opera Turandot (*) sound ominously in the distance. Note that the aria end with “Vincerò!” (= I will win)
Most commentators judged that White had to play 26. Bd4. Instead, Fabiano Caruana plays 26. c7. For a moment this looks promising. Magnus Carlsen sacrifices a piece with 26. … bxc7 followed by 27. Nxc7. With the White knight deflected the Black knight finally re-enters the game with 27. … ne5 hitting the queen and threatening a fork at d3. For example, if 28. Qe2 then nd3+ 29. Kd2 qa5+ getting the rook at c1 and picking up the knight at c7. The Black rook at a8 will go to c8 and lethal trouble will soon follow.
A better choice than 28. Qe2 was 28. Qd5. This threatens the Black rook at a8 (with check) if the Black rook at c8 captures the knight. But Black plays 28. … rab8. Now 29. … nd3+ is threatened with the White queen hanging, the white rook at h1 a possible victim to qf3+, the rook at c1 forked and the knight at c7 in serious danger.
In the actual game Fabiano Caruana played Nd5 again threatening the fork at e7. Magnus Carlsen plays … kh7 and Fabiano resigns: the queen is attacked, the rook will be forked when the knight checks at d3 and the White knight may be left hanging.
Stockfish suggests that 29. Qe2 is best – but it still rates a -4.07 (lost). There would follow … nd3+ 30. Kf1 nxc1 31. Ne7 qe5 32. 32. Qd1 Qxe7 33. Bxc1 Ra5
34. Kg2 Qb7 35. Rf1 Qd5 36. Bf4 Qxa2 37. Qd4 Qc4
38. Qxd6 Rb5 39. Qa3 Qd5 40. Be3 Rc2 41. Qxa4 Rbxb2)
- Turandot is a complex subject worthy of several blog entries. The opera was unfinished at the time of Giacomo Antonio Domenico Michele Secondo Maria Puccini’s death (born December 22 1858 ; died November 29 1924)