Imperialism, in its widest sense, is the exercise of unlimited rule over a vast extent of territory—such a sway as that at which Charlemagne aimed. Latterly, however, and especially in the United States, the term is used with reference to the policy of national expansion, and has been the cause of much controversy and conflict. Each acquisition of territory outside the continental limits of the United States has resulted in bitter criticism from the so-called anti-imperialists.