Needed for France to keep beating upon Germany during any mid-game. Ruhr and Burgundy and Germany is in trouble.
Ruhr: This small, triangular space is much more important than it looks for Germany's defense.
The Munich army would do well to move into Ruhr in the spring 1901 in preparation for Belgium in the fall. This can cause trouble though, if France moves armies to Burgundy and/or Picardy. Ruhr is crucial later as well; a common stalemate line passes next to Ruhr.
If France and Germany declare an uneasy truce, it is very likely that Germany will keep armies in Ruhr and Munich, France in Burgundy and/or Picardy, to prevent nasty stabs.
If France squeezes an army into Ruhr and continues attacking, Germany is in big trouble, especially if Holland has already fallen to France or England.