The concept of a “just war”, of intervention for humanitarian purposes in the historical perspective, of estimates by European politicians, intellectuals of the right to intervention with the aim of supporting “the principle of nationality” in the mid-19th century has been analyzed by researchers. However, specialists did not seem to adequately examine the understanding of the issue by contemporary Americans. The author of the article tries to trace the perception by “The United States Magazine and Democratic Review” of the principle of intervention in the context of the national movement in the Old World in the 1840-s. It is concluded that the journal paid great attention to the national organizations of the Italian, Irish, Polish and other nations, highly appreciated the works and activity of Henry Wheaton, an American jurist and diplomat. The mission, on behalf of the European power, of giving aid to the “oppressed nationalities” of the Old World by using military force was constructed. That mission was thought to be aimed at their political and national liberation. In rhetoric, it was connected with ideology. The right to intervention was not associated with the problem of extending freedom to slaves. On the whole, this “invented” American mission reflected partisan, political, sectional prejudices of the “Democratic Review” columnists, who were mainly radical Democrats, the followers of the U.S. President A. Jackson. During that period, the U.S. missionary role in relation to the European nations was mostly limited, in the imagination of the political writers, to the “exemplary” vision.