We should try instead 1. b5 Rb4 2. Ke6 Rxb5 3. Kd6 Rg5 (3. … Rxa5 4. Kc7 and the draw is easy to see)
Now the rook can go to g7, there will be an exchange of pawns, and the rook will be exchanged for the pawn to prevent (or to answer) promotion. White can force the issue before Black’s king can get over to secure things.
1. a6! ba (rxb4 2. a7) 2. b5!
1.b5 Rb4 2.Ke6 Rxb5 3.Kd6 Rxa5 4.Kc7 and draw.
re: anonymous 5:19
2. .. Rb4
and black wins, right?
1. a6 bxa
2. b5 Rb4 and now what?
We should try instead
1. b5 Rb4
2. Ke6 Rxb5
3. Kd6 Rg5 (3. … Rxa5 4. Kc7 and the draw is easy to see)
Now the rook can go to g7, there will be an exchange of pawns, and the rook will be exchanged for the pawn to prevent (or to answer) promotion. White can force the issue before Black’s king can get over to secure things.
a6??
I agree with jcheyne.
1.b4! (with the idea of 2.a6 pxp 3.b7 and white wins)
Black has two ways choices
a)1….Re5
b)1…Rb4
a)2.a6 Rxb5 (2..pxp 3.pxp and white wins)
3.a7 Ra5
4.Ke7 and white wins.
So, a) is no good for white.
b)2.Ke6 Rxb5
3.Kd6 Rh5 (3…Rxa5 4.Kc7 draws)
4.Kc7 Rh7+
5.Kb8 Kg2
6.Ka7 Kf3
7.a6 bxp+
8.Kxp and it’s a draw.