At the Potsdam Conference held in the Cecilienhof Palace between 17th July and 2nd August 1945, the "Big Three" powers confirmed the division of Germany (including Berlin) into four military occupation zones — France in the southwest, Britain in the northwest, the United States in the south, and the Soviet Union in the east.
(The Yalta Conference of February 1945 had already agreed that France would have its own zone but the territory would have to come from the US and British areas and not the Soviet.)
The photograph (taken by the US Army) shows delegates arriving at the Cecilienhof Palace.
The finally agreed zones of occupation involved some movement of British and US troops from their final combat positions.
The British withdrew from the green area (large areas of Mecklenburg) in late May 1945.
This map shows the emerging shape of post war Germany following the withdrawal of Anglo-American forces from areas that were to become part of the Soviet zone of occupation.......the lilac area in July/August 1945 and the light blue areas of Czechoslovakia and Austria in December 1945.
This was the shape of Germany until 1989 when the Berlin Wall and Inner German Border were removed.
In September 1990 (more than 45 years since the end of the war) the Treaty on the Final Settlement With Respect to Germany or the Two Plus Four Agreement was signed in Moscow. One element of the treaty, which led to reunification in October 1990, was to define the borders of Germany (see below).
This interesting map shows the results of much suffering and millions of deaths on the final shape of Germany.
Map credit: Uncensored History