We shall begin with a review of the relevant literature on national identity, with a special focus on the dichotomy of primordialism vs. constructivism, and that of cultural nation vs. political nation. We then examine the historical development of Alsace-Lorraine from the Roman Empire, the French Revolution, the Franco-Prussian War, through World War II. In the following, we look into how the Second German Empire undertook assimilation in the newly acquired territories. After World War I, Alsace-Lorraine was returned to France, and the Alsatians and the Lorrainians had to accommodate themselves to practices of reintegration, including linguistic assimilation and educational rectifications. During World War II, Nazi Germany retook the lands and enforces linguistic-cultural Germanisation and de-Frenchification. After the War, residents of Alsace-Lorraine have yet to face reintegration again in addition to political purges, which renders their identity choice dangling from ethnic, linguistic, regional, national, to European one.