One of the major problems facing independence movements in the USSR is that significant and increasing numbers of people reside outside their national homelands and, therefore, are considered aliens in the national homelands of others. The ancestral homeland is intimately enmeshed with nationalism, and the deep emotional attachment to and the sense of exclusive ownership of the sacred soil of the homeland should not be underestimated. Most ethnic conflict involves alien in-migration or disputes over the control of the homeland. Significant numbers of nonindigenous groups within the national homelands undermine the nation's exclusive claim to the homeland, dilute the national homogeneity of the homeland, and increase interethnic interaction within the homeland. Thus, throughout the world, nations strive to maximize national homogeneity within their homelands, and migration that results in alien incursions into the national homeland is viewed with alarm and frequently results in violence. In the Baltic republics, for example, alien in-migration is of intense public and political concern and is frequently cited as a major justification for political independence. Differential natural increase among the nationalities in a homeland is also a vital concern when it significantly affects the ethnic composition of a homeland. Assimilation through intermarriage is another development frequently viewed as a threat to national homogeneity, although in the Soviet Union offspring of intermarriage in national homeland most often identify with the indigenous nationality.