It was this theory, simple and even meaningless as it appears at first
sight, that gave the key to the practical work of framing a modern war plan
and revolutionised the study of strategy. It was not till the beginning of
the nineteenth century that such a theory was arrived at. For centuries men
had written on the "Art of War," but for want of a working theory their
labours as a whole had been unscientific, concerned for the most part with
the discussion of passing fashions and the elaboration of platitudes. Much
good work it is true was done on details, but no broad outlook had been
obtained to enable us to determine their relation to the fundamental
constants of the subject. No standpoint had been found from which we could
readily detach such constants from what was merely accidental. The result
was a tendency to argue too exclusively from the latest examples and to
become entangled in erroneous thought by trying to apply the methods which
had attained the last success to war as a whole. There was no means of
determining how far the particular success was due to special conditions
and how far it was due to factors common to all wars.

It was the Revolutionary and Napoleonic wars, coinciding as they did with a
period of philosophic activity, that revealed the shallowness and empirical
nature of all that had been done up to that time. Napoleon's methods
appeared to his contemporaries to have produced so strenuous a revolution
in the conduct of land warfare that it assumed a wholly new aspect, and it
was obvious that those conceptions which had sufficed previously had become
inadequate as a basis of sound study. War on land seemed to have changed
from a calculated affair of thrust and parry between standing armies to a
headlong rush of one nation in arms upon another, each thirsting for the
other's life, and resolved to have it or perish in the attempt. Men felt
themselves faced with a manifestation of human energy which had had no
counterpart, at least in civilised times.