Complex sentence: There was a huge quantity of allied military vehicles throughout France in various states and conditions, whose main purpose to the German army to this point had been to use them as symbols of Germany's victory.
Split into simpler sentences: There was a huge quantity of allied military vehicles throughout France in various states and conditions. As to the wrecks and other vehicles left behind, to this point the primary use the German army found of these vehicles was to use them as a symbol of Germany's victory.