In the process of nation-building, states attempt to make the state and the demographic nation overlap. In this process, national minorities become a problem and European nation states have a checkered past in terms of dealing with them, with variable policies reflecting ethnic antipathy at one moment and cooperation at another. Conventional wisdom holds that ethnic antipathy is the result of cultural distance or "age-old ethnic hatreds." However, according to Harris Mylonas, these theories neither predict outcomes nor account for variation in minority policy over time. His research focuses on the relationship between minority treatment and interstate relations, in an effort to gain a broader understanding the complexity of state-building and minority policies in Europe.

Mylonas presented three broad categories within which minority policies can fall: assimilation, accommodation, and exclusion. Each of these categories includes a variety of policies, but the unifying characteristics are that in assimilation, the state attempts to include the minority in its vision of the nation; in accommodation, the state makes space for a minority but maintains distance from the titular nation; and in exclusion, the minority is removed from the state. From his research of Serbia's minority policies over time, Mylonas found that all three types of policies were applied at various times. This suggests that cultural distance between Serbs and Albanians does not explain poor treatment of minorities.

His theory to explain this variability focuses on Serbia's external relations. Mylonas posits that a nation will exclude a minority when it is seen as a threat and will accommodate or assimilate a minority when the perceived threat to the state is reduced. In this framework, a national minority is seen as threatening when it is backed by a rival state, minority policy will be either exclusionary or accommodating, depending on the relative power of the state and its rival. If the state mobilizing the minority becomes an ally, minority policies will predictably shift from exclusion or accommodation to assimilation.

As an example and test case, Mylonas referred to Serbia's relations with its Kosovar-Albanian minority between 1913 and 1940. During this period, Kosovar Albanians had varying external support, and Serbian-Albanian relations changed from rival to ally. In 1913, the Kingdom of Serbia was eager to gain more access to the Adriatic, which aggravated relations with Albania. According to the theory, Mylonas would predict that the Serbian government would practice exclusionary policies, and the historical record backed up this prediction. Of course, this was not the only round of the game. After World War I, when Serbs felt secure since they were on the side of the victors, even though Kosovar Albanians were supported by the Kacak movement and Albania was a rival power, Serbian policies moved away from exclusion to assimilation. By 1924, when King Zogu took control of Albania and crushed the Kacak movement, Serbian King Aleksandar began to view Albania as an ally, and state policy towards the Albanian minority moved toward accommodation. This relatively peaceful period ended when Mussolini began his move to dominate the Adriatic by coopting Albania, which once again became a rival to Serbia, and moving Serbia's policy toward its Albanian minority back to assimilation.

This theory endeavors to show that nation-building policies do not simply reflect cultural distance between ethnic groups, but rather that the international relations have a substantial impact on minority policies. Mylonas offered several policy implications of his findings. First, in order to improve relations between minorities and the host country, the interstate relations must be improved. Second, in order to increase the chances for accommodation of minorities, states should build interstate alliances. Finally, states that are considered rivals of states housing a national minority should realize that attempting to assist that minority may put it in danger by prompting the other state to impose exclusionary policies towards its minority.