The Republics of the Soviet Union or the Union Republics (Russian: союзные республики, soyuznye respubliki) of the Soviet Union were ethnically-based administrative units that were subordinated directly to the Government of the Soviet Union. The Soviet Union was a highly centralized state.

According to the Article 76 of the Soviet Constitution, the sovereign Soviet socialist states united to become the Union of Soviet Socialist Republics. Article 81 of the Constitution stated that "the sovereign rights of Union Republics shall be safeguarded by the USSR".

In the final decades of its existence, the Soviet Union officially consisted of fifteen Soviet Socialist Republics (SSR). All of them were considered to be Soviet socialist republics (SSR), and all of them, with the exception of the Russian SFSR (until 1990), had their own Communist parties, part of the Communist Party of the Soviet Union.

Outside the territory of the Russian SFSR, the republics were constituted mostly in lands that had formerly belonged to the Russian Monarchy and had been acquired by it between the 1700 Great Northern War and the Anglo-Russian Convention of 1907.

Adolf Hitler (German: [ˈadɔlf ˈhɪtlɐ] ( listen); 20 April 1889 – 30 April 1945) was an Austrian-born German politician and the leader of the National Socialist German Workers Party (German: Nationalsozialistische Deutsche Arbeiterpartei (NSDAP), commonly referred to as the Nazi Party). He was chancellor of Germany from 1933 to 1945 and dictator of Nazi Germany (as Führer und Reichskanzler) from 1934 to 1945. Hitler is commonly associated with the rise of fascism in Europe, World War II, and the Holocaust.

A decorated veteran of World War I, Hitler joined the German Workers' Party, precursor of the Nazi Party, in 1919, and became leader of the NSDAP in 1921. In 1923, he attempted a coup d'état, known as the Beer Hall Putsch, in Munich. The failed coup resulted in Hitler's imprisonment, during which time he wrote his memoir, Mein Kampf (My Struggle). After his release in 1924, Hitler gained popular support by attacking the Treaty of Versailles and promoting Pan-Germanism, antisemitism, and anticommunism with charismatic oratory and Nazi propaganda. After his appointment as chancellor in 1933, he transformed the Weimar Republic into the Third Reich, a single-party dictatorship based on the totalitarian and autocratic ideology of Nazism. His aim was to establish a New Order of absolute Nazi German hegemony in continental Europe.