It is invariably a defense against the concerted aggressions of other patriots.

Taken in the large, the common defense of any given nation becomes a detail of the competitive struggle between rival nationalities animated with a common spirit of patriotic enterprise and led by authorities constituted for this competitive purpose.
Except on a broad basis of patriotic devotion, and except under the direction of an ambitious governmental establishment, no serious international aggression is to be had.

The common defense, therefore, is to be taken as a remedy for evils arising out of the working of the patriotic spirit that animates mankind, as brought to bear under a discretionary authority; and in any balance to be struck between the utility and disutility of this patriotic spirit and of its service in the hands of the constituted authorities, it will have to be cancelled out as being at the best a mitigation of some of the disorders brought on by the presence of national governments resting on patriotic loyalty at large.
But this common defense is by no means a vacant rubric in any attempted account of modern national enterprise.

It is the commonplace and conclusive plea of the dynastic statesmen and the aspiring warlords, and it is the usual blind behind which events are put in train for eventual hostilities.

Preparation for the common defense also appears unfailingly to eventuate in hostilities.