acirce: Very instructive endgame. Some annotations from Shereshevsky's "Endgame Strategy" starting with the position after move 16:
<White has the advantage. The difference in strength between the white knight and the black bishop is obvious. But to realize his advantage he must:
(a) fix Black's K-side pawns, since otherwise the bishop may escape from its 'prison';
(b) wrest the d-file from the opponent (in doing so he must weigh up whether or not the minor piece ending is won or whether a pair of rooks must be retained);
(c) give Black a second weakness on the Q-side, since he already has one, and a very serious one at that - the bishop on g7;
(d) if possible, invade the opponent's position with decisive effect.>
<White begins the battle for the d-file, exploiting the fact that 17..c4 loses a pawn to 18.Nd6.>
<The two players centralize their kings. White is not tempted into winning a pawn by 18.Ng5 Ke7 19.Nxh7 Bh6 20.h4, after which his knight is exchanged.>
<19..c4 was now threatened.>
<We give here Alekhine's commentary on this position:
"Black cannot exchange rooks, since after 21..Rd8 22.Rxd8 Kxd8 White wins as follows:
1st phase: 23.h4 followed by g2-g4 and g4-g5, against which Black has nothing better than ..h5, since the exchange of pawns will give the white knight the square h4.
2nd phase: b2-b3 followed by Kd3, Nc3 and Ke4.
3rd phase: the transfer of the knight to d3, which ties the black king to d6, in order to hold the twice-attacked e5 pawn.
4th phase: finally f2-f4, forcing the win of the g- or e-pawn, after which White wins easily.
By avoiding the exchange of rooks Black makes his opponent's task more difficult.">
<White sets about creating weaknesses on the Q-side. Since 23..a5 is not possible due to the loss of a pawn after 24.Rb3, the opening of the a-file is inevitable. This file will be occupied by the white rook, and this will become Black's second weakness.>
<Now after the exchange of rooks White could carry out his winning plan, but for this there is no necessity. At the moment his rook occupies an ideal position, and he has a quicker way to win.>
<Do not hurry! Black is deprived of the slightest counter-play, and so before the decisive offensive White 'packs in' the bishop at g7 by h2-h4 and g2-g4-g5.>
<The start of the concluding attack.>
<45..Kb7 loses to 46.Nd6+ and 47.Ne8, while if 45..Rf7 46.Rc8+.>