The Greeks overseas 4th ed.

"In Ancient Greece, colonies were sometimes founded by vanquished people, who left their homes to escape subjection at the hand of a foreign enemy; sometimes as a sequel to civil disorders, when the losers in internecine battles left to form a new city elsewhere; sometimes to get rid of surplus population, and thereby to avoid internal convulsions; and sometimes as a result of ostracism. But in most cases the motivation was to establish and facilitate relations of trade with foreign countries and further the wealth of the mother-city (in Greek, metropolis)."--Wikipedia.