Soviet Union was a nation in Europe.
During Second World War, the Soviet Union lost the rest of Sakhalin to Japan, portions of Central Asia were lost to China, and did not gain any land from Finland. However, the Soviet Union managed to gain the Baltics and some other lands, and annexed them. The Soviet Union managed to win the war in Europe with other allies, and in 1946 the Soviets made peace with Japan. After the Second World War, the Cold War began.
During the Cold War, the Soviets funded the communists in Portuguese-held Angola and managed to establish a decent influence over Eastern Europe and parts of Middle East and Africa, along with Cuba.
However, by 1986, most of the Soviet's puppets broke away, and soon in 1988, Kazakhstan, Tajikistan, and Ukraine broke away as did Moldova. Afterwards, the Soviet Union managed to last until 1991, when it was succeeded by the Russian Federation.