April 1949, the French began to merge their zone into Bizonia, which became Trizonia.
May 1949, Trizonia became the Federal Republic of Germany (FRG/BRD) with Bonn as the provisional capital.
October 1949, the Soviet zones (Germany and Berlin) became the German Democratic Republic (GDR/DDR) with Berlin as the capital.
West Germany (FRG/BRD) and East Germany (GDR/DDR) with their respective capitals (Bonn & Berlin)
The border between Trizonia and the Soviet sector became an international border but was comparatively easy to cross.
Since the end of the war in 1945 there had been a constant flow of population from east to west. Between October 1945 and June 1946, 1.6 million Germans left the Soviet zone.
The border between the Soviet Zone and the other Allied Zones was known as the 'Green Border'. Athough it was demarcated and monitored, it was relatively easy to cross (especially in rural areas).
With the foundation of the FRG (West Germany) and GDR (East Germany) this movement continued. The number of Soviet soldiers on the border was increased and supplemented with border guards from the newly established East German Volkspolizei ("People's Police"). Many unofficial crossing points were blocked with ditches and barricades. Despite these increased security measures, 675,000 people fled to West Germany between 1949 and 1952.
Note: It is important to remember that, although West and East Germany became separate countries, East Germany (until 1954) remained officially under Soviet Occupation.
In West Germany, occupation continued until 5 May 1955 when the 'General Treaty' (Deutschlandvertrag) entered into force.
After these dates, NATO and Soviet forces remained to represent their respective interests.