I happened to be looking at the otherwise unremarkable game Rodriguez Crespo (1904)-Kolar (2196), August Open Cambre ESP 2006, when I arrived at the following position:
White has been trying to make something of his good-bishop versus bad-bishop advantage in a typical French ending, but Black seems to be holding. (A couple of moves earlier, White made the mistake of allowing the Black bishop to get out to h5.)
Now things start to get interesting, however.
44...Nf7? (44...Kf7 45.Ng2 Ng6 and Black should be fine.)
45.Ng2! Aiming for f4, forking the h5-bishop and the e6-pawn. Now Black is in trouble.
45...Bg6? (45...Ng5 46.Nf4 Bf7 47.h4 Nh7 48.Kg4 Nf8 seems to hold for Black. White has no way of breaking through.)
46.Bxg6 Kxg6 47.Kg4? (47.h4! wins, not letting the Black knight out via g5. Black is running out of moves and the White knight will start to eat up his pawns. For example, 47...Kf5 48.Kf3 Nh8 49.Ne3+ Kg6 50.Ng4 Kg7 51.Nf6 Ng6 52.Kg4 Nf8 53.Kh5. Now it is a draw again.)
47...h5+ 48.Kf4 Ng5 49.h4 Ne4 Wait a minute, you must be asking, how can this be a draw? Isn't White going to lose his pawn on a4?
51.Nc2?? The losing move! White has the amazing drawing resource 51.Kf3! Nxa4 52.Nd1!!
Now the Black knight cannot move without being captured and the Black king has no way to break through. White has established a fortress and the game is a draw! For example, 52...Kf5 53.Ne3+ Kg6 54.Nd1 and Black has made no progress. If the Black king goes to the queenside, hoping perhaps to play ...Nc5 and pick up a couple more pawns for the knight, then White just captures the pawn on h5.
After missing this chance, White goes down to defeat in a couple of moves.
51...Nxa4 52.Na1 Nc3 0-1
20 hours ago