Active King

In a ten minute game this morning, I struggled most of the game for equality. When my opponent erred in opting for a rook ending, rather than knight vs. bishop when his passed pawn likely would have cost me my bishop, I knew my drawing chances were good.

Then, while reviewing the game, I was surprised to see that a move that assured the draw was deemed an error by the website's game analysis feature.

Let's look at the critical position with normal diagrams (White on bottom).

White to move

I played 47...Kxf4, reaching an easily drawn ending that neither side should have difficulty playing.

This position, however, is winning for Black.

47...Rb2+ 48.Kf1 (Kg1 likely transposes) 48...Kf3

Leaving the f-pawn alone while creating mate threats was completely off my radar, perhaps because I knew there was no forced checkmate. The threats, however, gain something.

49.Kg1 Rb8+ 50.Kh2 Kf2

White to move

White is forced to move the rook and cannot attack my g-pawn.

51.Rh8 Rxb7 52.Rh6 Re7 

Black keeps mate threats alive.

53.Kh1

Black to move

Two of the roads that lead to victory from here are:

a) 53...Re6 54.Rh2+ Kg3 55.Rg2+ Kxf4 finally capturing the f-pawn!
b) 53...g5! 54.Rh2+ (54.fxg5 Kg3 and White must give up the rook to avoid checkmate) 54…Kf3

White to move

Black's g-pawn is untouchable due to the mate threat.

55.Rb2 Re1+ 56.Kh2 g4

I would have known that I was winning had I foreseen that I could reach this point.

It was good to draw a 2000+ rated player, but there was an instructive missed opportunity that I hope to remember.