Note 21 — Chapter VI · HOW GENERAL VON KLUCK AVERTED RUIN
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The late General Hamley, describing what he considered the most effective lines for an invasion of France from Germany in opposition to the defensive adopted by Napoleon, points out that if the left of the defence threatens the invaders' communications, the invaders, leaving their right on the Ourcq and Marne, march through Sezanne to fight on the right bank of the Seine. Pushing the French right and centre to the Yères with their own centre and left, they fight then the decisive battle. It should be decisive, for the [Germans] on the two rivers, approaching each other in the narrowing angle can combine in a movement on Paris, holding the passages at Melun and Montereau on the one side, and at Meaux on the other.
"In executing such a plan the weapons of the defender would be in some measure turned against himself.... But the assailants in taking these forward steps do so at the disadvantage of attacking a strongly posted enemy and under penalty of exposing a flank to him. This course demands a superiority in numbers of not less than 4 to 3, and probably greater than that."
The Germans had adopted this very plan, but they had not the superiority they imagined.