A state’s integration of its new residents often fails. People’s sense of identity can become deterritorialized and may be driven by long-distance nationalism, in which ties with compatriots in the far-off country of origin are emphasized over those with neighbors in the new country of residence. Meanwhile, the countries of origin of these migrants may aim at diaspora engagement in an attempt to leverage this deterritorialized sense of belonging. This chapter analyzes such diaspora engagement. It distinguishes between various kinds of diaspora—victim, labor, imperial, and trade diasporas—and shows how the purposes of diaspora also vary, from the purely cultural to the economic. The chapter notes that diasporas could become a security issue between the country of residence and country of origin, depending on their bilateral political relationship.