The United States, the United Kingdom, and the Soviet Union had agreed at Potsdam to a broad program of decentralization, treating Germany as a single economic unit with some central administrative departments. These plans never materialised, initially because France blocked any establishment of central administrative or political structures for Germany; and also as both the Soviet Union and France were intent on extracting as much material benefit as possible from their occupation zones in order to make good in part the enormous destruction caused by the German Wehrmacht; and the policy broke down completely in 1948 when the Russians blockaded West Berlin and the period known as the Cold War began.