johnlspouge: Here is computer-assisted analysis from Toga II 1.3.1 and me. I apologize in advance for its length. Believe me, I wish it did not feel like Sunday.
Friday (Difficult): White to play and win.
Material: Down a P. White has 2Bs bearing down on the Black K-side, with Qd1 and Re1 on open files. The White Nc3 requires activation, but all other White pieces except Ra1 are ready to attack. The Black Q-side is undeveloped, and many Black pieces are misplaced for K-side defense, particularly Na4, Ra8, and Bc8. The Black K-side defense rests largely with Nf6. The White Nf5 is the salient feature of the position, but Pe6 threatens it.
Candidates (13.): Nxg7, Ne4, Nh6+
13.Nxg7 (threatening 14.Nh5, denuding the Black K-side)
Black can accept the sacrifice.
(1) 13…Kxg7 14.Bh6+
Again, Black can accept the sacrifice.
(1.1) 14…Kxh6 15.Qd2+
(1.1.1) 15…Kh5 16.Re3 (threatening 17.Rh3+ and mate soon)
16…Qxh2+ 17.Kxh2 Ng4+ 18.K moves
White has material advantage and a huge attack.
(1.1.2) 15…Kg7 16.Qg5+ Kh8 17.Qxf6+ Kg8 18.Bxh7+ Kxh7 19.Re4,
and mate soon.
(1.2) 14…Kh8 15.Qd4
(1.2.1) 15…Be7 16.Bxf8, regaining material with the attack.
(1.2.2) 15…Qd8 16.Bg5 Kg7 17.Qh4,
threatening 17.Bxf6+ Qxf6 18.Qxh7#
18…h5 18.Bh6+ Kxh6 [else, mate soon]
19.Qf4+ Kg7 20.Qg5+ Kh8 21.Qh6+ Kg8 22.Re5,
then 23.Rxh5 24.Qh7#
(1.3) 14…Kg8 15.Qf3,
threatening 16.Qxf6, 16.Ne4, and possibly 16.Qg3+ and 16.Qg4+
(1.3.1) 15…Bxc3 16.bxc3 Ne8 17.Qg4+ Kh8 18.Bxf8, gaining material
(1.3.2) 15…Ne8 16.Bxh7+ Kxh7 17.Bxf8,
regaining material with the attack, because of
17…Bxf8 18.Qxf7+ then 19.Re3
threatening 20.Rh3, so Black hemorrhages material.
Black can decline the sacrifice.
according to Toga, the best way to decline the sacrifice, but the exchange of Pc4 and Ng7 for Pg7 and Nf6 must produce a winning attack for White.