In 1955, the Federal Republic of Germany (FRG) and the Soviet Union establish diplomatic relations in exchange, notably, for the liberation of the final German prisoners of war detained in the Soviet Union. In the same year, the ‘Hallstein Doctrine’, named after Walter Hallstein, State Secretary to the Foreign Minister, is established, under which the FRG refuses to maintain diplomatic relations with States that recognise the existence of the German Democratic Republic (GDR), with the exception of the Soviet Union.