Irredentism (from Italian irredento for "unredeemed") is any political or popular movement intended to reclaim and reoccupy an area that the movement's members consider "lost" or "unredeemed". These territorial claims are justified on the basis of real or imagined national and historic (an area formerly part of that state) or ethnic (an area inhabited by that nation or ethnic group) affiliations. It is often advocated by nationalist and pan-nationalist movements and has been a feature of identity politics and cultural and political geography.
An area that may be subjected to a potential claim is sometimes called an irredenta. Not all irredentas are necessarily involved in irredentism.
The word was coined in Italy from the phrase Italia irredenta ("unredeemed Italy"). This originally referred to rule by Austria-Hungary over territories mostly or partly inhabited by ethnic Italians, such as Trentino, Trieste, Gorizia, Istria, Rijeka and Dalmatia during the 19th and early 20th centuries.
A common way to express a claim to adjacent territories on the grounds of historical or ethnic association is by using the adjective "Greater" as a prefix to the country name. This conveys the image of national territory at its maximum conceivable extent with the country "proper" at its core. The use of "Greater" does not always convey an irredentistic meaning.
Some states formalize their irredentist claims by including them in their constitutional documents, or through other means of legal enshrinement.
The Afghan border with Pakistan, known as the Durand Line, was agreed to by Afghanistan and British India in 1893. The Pashtun tribes inhabiting the border areas were divided between what have become two nations; Afghanistan never accepted the still-porous border and clashes broke out in the 1950s and 1960s between Afghanistan and Pakistan over the issue. All Afghan governments of the past century have declared, with varying intensity, a long-term goal of re-uniting all Pashtun-dominated areas under Afghan rule.