The Inevitability of War - in two sentences.

"There is no exception to the rule that every organic being naturally increases at so high a rate, that if not destroyed, the earth would be covered by the progeny of a single pair."

"...the struggle[for existence] almost invariably will be most severe between the individuals of the same species, for they frequent the same districts, require the same foods, and are exposed to the same dangers."

Charles Darwin: On the Origin of Species, 1859.