Irredentism

political idea of reclaiming areas

Irredentism is the desire of a state, or of some people in a state, for annexation of land that another state has. The ones who want the land say it really belongs to them because the other state stole it, or because they wish to liberate people of the same ethnicity or other connection who live there. The term was invented in the 1870s when the unification of Italy left some Italian people in places ruled by someone else.