Endgame puzzle

@fmdavidhlevin said
I've found it beneficial to find and analyze all checks, captures, and moves that position a chessman to subsequently check, capture, or do something threatening.

After 1. d4+ Kb6 2. c5+ Kb5 3. c6 Kb6, does White have any moves that fall within one of the above categories?

@kilroy70 said
After ...King-b6

c7, Rc2
d6, Rc6
d7, Rxc7
d8 (queen)

White appears to be unstoppable after d6

@fmdavidhlevin said
I think you've got it!

SOLV'D

Before the diagrammed position, Black indeed should have played ...Kd7. He underestimated the strength of the white pawn mass.