 Federations may foster peace, in the senses of preventing wars and preventing fears of war, in several ways. States can join a (con)federation to become jointly powerful enough to dissuade external aggressors, and/or to prevent aggressive and preemptive wars among themselves. The European federalists Altieri Spinelli, Ernesto Rossi and Eugenio Colorni argued the latter in the 1941 Ventotene Manifesto: Only a European federation could prevent war between totalitarian, aggressive states. Such arguments assume, of course, that the (con)federation will not become more aggressive than each state separately, a point Mill argued.