I had Black against Julien Shepley (to move) in this pawn ending from an RTCC arena game the other day.
I asked you to analyse 40. Kf3 and 40. Kd3.
The answer in brief is that 40. Kf3 draws, as do 40. b5 and, perhaps less obviously, 40. g4. For instance, 40. Kf3 a6 41. g4! f4 42. Ke4!
The game continued 40. Kd3? a5? 41. bxa5 bxa5 and the game was soon drawn.
I could have won, though. 40. Kd3? a6! (the only winning move, threatening b5 to prevent White securing a protected passed pawn) 41. c5+ bxc5! 42. dxc5+ Kd5! or Ke5! and Black will secure the full point.
Very instructive, I think. A position well worth studying in depth. It’s so important – and so difficult – to excel at pawn endings.