detachment, more or less complete in itself, organized for some
particular purpose (e.g. to cover a siege), and placed for the time
being under some general officer other than the chief commander. The
modern army corps is a development from the division of all arms, which
originated in the French Revolutionary wars. It is a unit of
considerable strength, furnished with the due proportion of troops of
all arms and of the auxiliary and medical services, and permanently
placed under the command of one general. The corps organization (though
a _corps d'armee_ was often spoken of as an _armee_) was used in
Napoleon's army in all the campaigns of the Empire. It may be mentioned,
as a curious feature of Napoleon's methods, that he invariably
constituted each _corps d'armee_ of a different strength, so that the
enemy would not be able to estimate his force by the simple process of
counting the corps flags which marked the marshals' headquarters. Thus
in 1812 he constituted one corps of 72,000 men, while another had but
18,000. After the fall of Napoleon a further advance was made. The
adoption of universal service amongst the great military nations brought
in its train the territorial organization, and the corps, representing a
large district, soon became a unit of peace formation. For the smooth
working of the new military system it was essential that the framework
of the war army should exist in peace. The Prussians were the first to
bring the system to perfection; long before 1866 Prussia was permanently
divided into army corps districts, all the troops of the III. army corps
being Brandenburgers, all those of the VI. Silesians, and so on, though
political reasons required, and to some extent still require,
modifications of this principle in dealing with annexed territory (e.g.
Hanover and Alsace-Lorraine). The events of 1866 and of 1870-71 caused
the almost universal adoption of the army corps regional system. In the
case of the British army, operating as it usually did in minor wars, and
rarely having more than sixty or seventy thousand men on one theatre
even in continental wars, there was less need of so large a unit as the
corps. Not only was a British army small in numbers, but it preserved
high traditions of discipline, and was sufficiently well trained to be
susceptible as a unit to the impulse given by one man. Even where the
term "corps" does appear in Peninsular annals, the implication is of a
corps in the old sense of a grand detachment. Neither cavalry nor
artillery was assigned to any of the British "corps" at Waterloo.