Key-Squares in Pawn Endgames In an instructional video, I have found this position:



The instructor (Dr Muller) says about key squares that are marked with green. I am unable to get the idea behind how Dr Muller determined these squares as Key Squares. I have practiced it many times in Fritz but fail to understand the exact technique that I should employ. The instruction goes rather fast and not helpful for beginners.

Please help me to proceed as white from here.
If the white king reaches one of the green key squares, then white will win. There is no rule determining those squares, just concrete analysis. However, once we have the key squares in place, we can systematically search for pairs of corresponding squares.


If the white king is on d8, then the black king must move to f8.
If the white king is on d7, then the black king must move to f7.
If the white king is on d6, then the black king must move to f6.
If the white king is on c8, then the black king must move to e8.
If the white king is on c7, then the black king must move to e7.
If the white king is on c6, then the black king must move to e6.


If at any stage black to move has the king already placed on the square corresponding to the square of the white king, black is in zugzwang and will lose.

This example turns out to be a quite simple case of (distant) opposition and 1. Kb7! wins for white.