The Soviets tried to drive the western allies out of West-Berlin twice, once in 1948 and again under Chrutsjev in 1956. Both times a blockade was broken by an airlift. Because of its status as an all allied occupied city, Berlin was the only place where Germans could freely travel from East to West. The border between the Federal Republic and the G.D.R. was fortified and barricaded. Great numbers of G.D.R. inhabitants left the country through Berlin. In 1961 the G.D.R. government erected a wall separating East and West Berlin and turned the G.D.R. with East-Berlin into a hermetically closed country. The Soviets declared their occupation of Berlin to be over and handed it over to their G.D.R. satellite state. Later an agreement between the allies reaffirmed East-Berlin as the Soviet zone of an all allied occupied Berlin. The parties agreed to disagree about the wall and the status of the two parts of the city towards the two German states.
In the early 1970's a period of relaxation in the Cold War induced the Federal Republic to open ties to Eastern European countries including the G.D.R. The first Social Democrat Federal Chancellor, Willy Brandt, initiated the opening of relations with the G.D.R. on the basis that the Federal Republic would not view the G.D.R as a foreign country but as a part of Germany as a whole, in reference to the rights the allies still held towards Germany as a whole. The G.D.R. politely disagreed but entered into the treaty just the same. Willy Brandt also went to Warsaw and Moscow and signed treaties in which the Federal Republic recognised the post-war borders, giving up their claim to the territories that were placed under Polish and Soviet administration by the allied government in 1945.
A ferocious political and judicial battle within the Federal Republic was the consequence. The Federal diet ratified the treaties, but the State of Bavaria challenged the treaties in the Federal Constitutional Court in Karlsruhe. Bavaria's challenge was thrown out, but the court ruled that the Federal Republic might very well recognise Poland and the Soviets Union’s post war borders, but could in this matter only speak for itself as a part of Germany and not for Germany as a whole, a concept theoretically still in existence where International Law was concerned, because of the enduring rights and responsibilities that the allies still held over it. In other words, the Federal Republic was not entirely identifiable with Germany. There were the allies and now too the G.D.R. to be reckoned with. The court made an elaborate compromise. All allied powers had recognised the new borders and so had the G.D.R. The court’s verdict however, enabled conservatives to claim that the lost provinces were still theoretically a part of the German Realm, as it enabled liberals and social democrats to take the view that they were now lost and a part of Poland and the Soviet Union as far as the Federal Republic was concerned.