first class, instances are frequent. The Romans acquired power by these
interferences, and the empire of the English India Company was assured
in a similar manner. These interventions are not always successful.
While Russia has added to her power by interference with Poland,
Austria, on the contrary, was almost ruined by her attempt to interfere
in the internal affairs of France during the Revolution.

Intervention in the external relations of states is more legitimate, and
perhaps more advantageous. It may be doubtful whether a nation has the
right to interfere in the internal affairs of another people; but it
certainly has a right to oppose it when it propagates disorder which may
reach the adjoining states.

There are three reasons for intervention in exterior foreign
wars,--viz.: 1, by virtue of a treaty which binds to aid; 2, to maintain
the political equilibrium; 3, to avoid certain evil consequences of the
war already commenced, or to secure certain advantages from the war not
to be obtained otherwise.

History is filled with examples of powers which have fallen by neglect
of these principles. "A state begins to decline when it permits the
immoderate aggrandizement of a rival, and a secondary power may become
the arbiter of nations if it throw its weight into the balance at the
proper time."

In a military view, it seems plain that the sudden appearance of a new
and large army as a third party in a well-contested war must be
decisive. Much will depend upon its geographical position in reference
to the armies already in the field. For example, in the winter of 1807
Napoleon crossed the Vistula and ventured to the walls of Königsberg,