When the League of Nations was called in to settle territorial disputes in the Middle East, their deliberations were guided by the ideology of self-determination. Assigning territory based on collective identity required that they identify mutually exclusive communities; enforcing the new lines would institutionalize those new intra-state boundaries. By comparing the Mosul Question (1925) and the Sanjak Question (1936), this paper will analyze the processes by which Europeans introduced new taxonomies of identity into the region, emphasized the desirability of dividing Adifferent@ collectives, and, in the process, encouraged the growth of animosities based on newly-important characteristics. The League of Nations sent a commission to Mosul, claimed by both the new Republic of Turkey and recently-independent Iraq. As they fanned out into the countryside, European commissioners sought to find out how the local population defined themselves: were they Arabs or Turks. For Ottoman subjects, the question seemed quite peculiar, and the population responded instead with specific information about the kind of government they would prefer. In the end, the commissioners recognized that identity did not correlate with the political demands of Mosul=s population, giving the province to Iraq for economic and strategic reasons instead. When France agreed to a Treaty of Independence with Syria in 1936, Turkey insisted that the autonomous province of Alexandretta must not be part of the new Syrian state. France agreed that Alexandretta would become a separate state federated with Syria. The League insisted that the parliament of the newly-independent Alexandretta would reflect the groups present in the local population. Registration for the elections was to serve also to indicate the relative proportions of seven groups that Europeans identified in the province: Turks, Arabs, Kurds, Alawis, Greek, Armenians, and Other. Registrations quickly turned violent, as the League agreed that each man could choose any affiliation. The new categories assumed identities and divisions that made little sense to local voters, who agreed with the Turkish contention that local identities were fluid. Both episodes begin with notions of identity that Europeans constructed as scientific, mutually-exclusive, and representative of the population=s essential nature. The ideology of self-determination, after all, depended on the ability to recognize and interrogate a collective self. In both of these cases, European-defined collectives encouraged local exclusivist nationalisms while discouraging older forms of group solidarity.