In his book, the author analyses the formation of territorial identities in a nineteenth century border region of Germany, the province of Posnania, and makes it a decisive factor in explaining the determination of the German-Polish border in contemporary times. He assumes that the abrupt reflow east-west of the Oder border at the end of World War II, after a long period of eastward displacement, is due to a deeper cause than the military defeat of Nazi Germany. Indeed, the contemporary border between Germany and Poland, where the recent treaties signed between the two countries since Germany was reunited, completed political recognition, marred a line of contact between two territorial identities, which were formed during the 19th century. The author interprets them as two nationalisms whose confrontation led to a process of ‘dissimilarity’ or impossible assimilation which led to Prusse’s failure in its political intention of territorial integration of this piece of Poland, which was broken down at the end of the 18th century. The author starts by tracing the steps...