w science of their use. When such is the case, science appears to
uninstructed opinion to have changed this ancient and fixed characteristic
which is in the very nature of war. But in fact there has been no such
change. Under the most primitive conditions an advantage of this type was
of supreme importance; under conditions the most scientific and refined it
is an advantage that may still be neutralised if the enemy has learnt
means of screening himself as excellent as our means of discovering him.
Even the aeroplane, whose development in the modern French service has so
vastly changed the character of information, and therefore of war, can
never eliminate the factor of which I speak. A service possessed of a
great superiority in this new arm will, of course, be the master of its
foe; but when the use of the new arm is spread and equalised among all
European forces so that two opposing forces are equally matched even in
this new discovery, then the old element of move and countermove, feint,
secrecy, and calculated confusion of an adversary, will reappear.[6]

In general, then, to point out the ignorance and the misconceptions of one
commander is no criticism of a campaign until we have appreciated the
corresponding ignorance and misconceptions of the other. We have already
seen Wellington taken almost wholly by surprise on the French advance; we
shall see him, even when he appreciated its existence, imagining it to be
directed principally against himself. We shall similarly see Napoleon
underestimating the Prussian force in front of him, and underestimating
even that tardy information which had reached Wellington in time for him
to send troops up the Brussels road, and to check the French advance along
it. But we must judge either of the two great opponents not by a single
picture of his own misconceptions alone, but by the combined picture of
the misconceptions of both, and especially by a consideration of the way
in which each retrieved or attempted to retrieve the results of those
misconceptions when a true idea of the enemy's dispositions was conveyed
to him.

* * * * *

Here, then, we have Napoleon on the morning of Friday the 16th of June
prepared to deal with the Prussians. It is his right-hand body, under
Grouchy, which is deputed to do this, while he sends up the left-hand
body, under Ney, northwards to brush aside, or, at the worst, at least to
hold off whatever of the Duke of