This famous quote by Magnus Carlsen has been used a lot and often a bit out of context. Of course, fortresses exist but sometimes they can be broken down.
In his excellent book Chess Endgames for Club Players (New In Chess 2022), IM Herman Grooten talks about this subject as well. His explanations are easy to understand and very valuable for players of all levels. In a chapter on fortresses, he looks at the famous ending between Timman and Nunn where Black was able to break down the fortress (which it really was…) with a little help from his illustrious opponent.
Then Herman was made aware of a very similar ending which was not a fortress but could have become one if the young and talented White player had read Herman’s book. Instructive errors were made and highlighted by our author. Please check it out for yourself and make sure to apply it in your own game!
The comments and analysis below are from Herman Grooten himself.