To uphold neighboring states whose existence is necessary either for the safety of the government or the balance of power;
To fulfill the obligations of offensive and defensive alliances;
To propagate political or religious theories, to crush them out, or to defend them;
To increase the influence and power of the state by acquisitions of territory;
To defend the threatened independence of the state;
To avenge insulted honor; or,
From a mania for conquest.
It may be remarked that these different kinds of war influence in some degree the nature and extent of the efforts and operations necessary for the proposed end. The party who has provoked the war may be reduced to the defensive, and the party assailed may assume the offensive; and there may be other circumstances which will affect the nature and conduct of a war, as,—
1. A state may simply make war against another state.
2. A state may make war against several states in alliance with each other.