Gau East Prussia was formed in 1933 in Nazi Germany

Nazi Germany

Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 initially as a district within the Free State of Prussia

Free State of Prussia (1933-1935)

The Free State of Prussia briefly continued to exist in name after take-over by the Nazi regime of Adolf Hitler. Unlike the Free State of Prussia that existed from 1918 to 1933 during the Weimar Republic, the Nazi Free State had no parliamentary democracy and was ruled exclusively under the...

. In 1935, Germany's constituent states were dissolved and the gaus replaced the states and their responsibilities.

In 1939, East Prussia expanded following the annexation of the Klaipėda Region

Klaipėda Region

The Klaipėda Region or Memel Territory was defined by the Treaty of Versailles in 1920 when it was put under the administration of the Council of Ambassadors...

 from Lithuania and the occupation of Poland, while a sliver of territory from the gau was transferred to Reichsgau Danzig-West Prussia

Reichsgau Danzig-West Prussia

The Reichsgau Danzig-West Prussia was a Nazi German province created on 8 October 1939 from the territory of the annexed Free City of Danzig, the annexed Polish province Greater Pomeranian Voivodship , and the Nazi German Regierungsbezirk West Prussia of Gau East Prussia. Before 2 November 1939,...

.

After Germany's attack on the USSR, the Belarusian city of Hrodna

Hrodna

Grodno or Hrodna , is a city in Belarus. It is located on the Neman River , close to the borders of Poland and Lithuania . It has 327,540 inhabitants...

  also became part of the gau.

After the war, the territory of the former gau became part of the RSFSR enclave of Kaliningrad

Kaliningrad

Kaliningrad is a seaport and the administrative center of Kaliningrad Oblast, the Russian exclave between Poland and Lithuania on the Baltic Sea...

 in the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

, major sections were given to Poland

Poland

Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...

, and the area of the Klaipėda Region was returned to the Lithuanian SSR

Lithuanian SSR

The Lithuanian Soviet Socialist Republic , also known as the Lithuanian SSR, was one of the republics that made up the former Soviet Union...

 and Hrodna

Hrodna

Grodno or Hrodna , is a city in Belarus. It is located on the Neman River , close to the borders of Poland and Lithuania . It has 327,540 inhabitants...

 - to the Belarusian SSR within the Soviet Union

Soviet Union

The Soviet Union , officially the Union of Soviet Socialist Republics , was a constitutionally socialist state that existed in Eurasia between 1922 and 1991....

.