In the heated days that herald the beginning of the WWI, much was discussed about the best strategy that the French should hold, considering mainly an German advance through Belgium - a neutral state.
Quoting Barbara Tuchman, on The Guns of August,
(...) To match numbers he believed the Germans would send through Belgium, General Michel proposed to double French front-line effectives by attaching a regiment of reserves to every active regiment. Had he proposed to admit Mistinguette to the Immortals of the French Academy, he could hardly have raised more clamor and disgust.
"Les resérves, c'ést zéro!" was the classic dogma of the French officer corps.
The reserves of France were "considered fit to only rear duty or for use as fortress trops". The attach of this reserves "would be to put a drag on the army's fighting thrust."
Some years later, on the beginning of the WWII, the "classic dogma" was to be remembered one more time, when France was surrounded by Germany. Quoting Winston Churchill, in Their Finest Hour,
The General [Gamelin] talked perhaps for five minutes without anyone saying a word. When he stopped there was a considerable silence. I then asked: "Where is the strategic reserve?" and, breaking to French, which I used indifferently (in every sense): "Où est la masse de manoeuvre?" General Gamelin turned to me and, with a shake of the head and shrug, said: "Aucune."
There was another long pause. Outside in the garden of the Quai d'Orsay clouds of smoke arose from large bonfires, and I saw from the window venerable officials pushing wheel-barrows of archives on to the. Already therefore the evacuation of Paris was being prepared.