Imperialism, its character, means and ends has changed over time and place. Historically, western imperialism, has taken the form of tributary, mercantile, industrial, financial and in the contemporary period, a unique militarist-barbaric form of empire building.
Within each period, elements of past and future forms of imperial domination and exploitation co-exist with the dominant mode. For example, in the ancient Greek and Roman empires, commercial and trade privileges complemented the extraction of tributary payments. Mercantile imperialism, was preceded and accompanied initially by the plunder of wealth and the extraction of tribute, sometimes referred to as primitive accumulation, where political and military power decimated the local population and forcibly removed and transferred wealth to the imperial capitals.