In Endgame theory, especially in King and Pawn endgames there is a concept known as Corresponding Squares (Sister Squares as mentioned by some Russian authors) which always seemed as quite a complex part of the endgame for me since my childhood. My memory vaguely wanders around some books by Jonathon Speelman and Averbakh. Personally, I have never had this concept in any of my endgames. I also, do not recall having even seen them in recent praxis. OfCourse Dvoretsky and Mueller have also dealt with this topic in their own endgame manuals in a very detailed manner.
In a recent game of Rasmus Svane, I happened to notice an endgame with four pawns for each side and his opponent having the better minor piece and a better placed King. My friend Thorsten Cmiel had shared the following position with a comment that it needed to be solved by the system of corresponding squares.
