CHAPTER II.
STRATEGY War has been defined, "A contest between nations and states carried on by force." But this definition is by some considered defective, inasmuch as it would exclude all civil wars.
When war is commenced by attacking a nation in peace, it is called _offensive_, and when undertaken to repel invasion, or the attacks of an enemy, it is called _defensive_.

A war may be essentially defensive even where we begin it, if intended to prevent an attack or invasion which is under preparation.

Besides this general division of war, military writers have made numerous others, such as-- _Wars of intervention_, in which one state interferes in favor of another.

This intervention may either have respect to the _internal_ or to the _external_ affairs of a nation.

The interference of Russia in the affairs of Poland, of England in the government of India, Austria and the allied powers in the affairs of France during the Revolution and under the empire, are examples under the first head.