The transfer of part of the territory and population of one state to another, whether pre-existing, or newly created. ‘The last act of the European geopolitical drama has yielded the greatest “advantage” for the former minorities in Central and Eastern Europe, but, as calculations show, the nation-state model became a less effective tool to solve ethnic problems, since each new secession engenders the appearance of new minorities’ (Kotossov and Treivish (1998) Polit. Geog. 17, 5). Writing on Biafra’s abortive secession in 1967, Diamond (2007) Dialec. Anthrop. 31, 1–3 observes that ‘Nigeria is not a nation but a political idea imposed by force of foreign arms. The variety of peoples within its borders will continue to seek accommodation.’ See Le Breton and Weber (2001) IMF WP/01/176, on ‘how to prevent secession’.