<P> Shortly before World War II, Stalin signed the Molotov--Ribbentrop Pact agreeing to non-aggression with Nazi Germany, after which the two countries invaded Poland in September 1939 . In June 1941, the pact collapsed as Germany turned to attack to the Soviet Union, opening the largest and bloodiest theatre of war in history . Soviet war casualties accounted for the highest proportion of the conflict in the effort of acquiring the upper hand over Axis forces at intense battles such as Stalingrad and Kursk . The territories overtaken by the Red Army became satellite states of the Soviet Union; the postwar division of Europe into capitalist and communist halves would lead to increased tensions with the West, led by the United States . </P> <P> The Cold War emerged by 1947, as the Eastern Bloc, united under the Warsaw Pact in 1955, confronted the Western Bloc, united under NATO in 1949 . On 5 March 1953, Stalin died and was quickly succeeded by Nikita Khrushchev, who in 1956 denounced Stalin and began the De-Stalinization of Soviet society through the Khrushchev Thaw . The Soviet Union took an early lead in the Space Race, with the first artificial satellite and the first human spaceflight . Khrushchev was removed from power by his colleagues in 1964 and was succeeded as head of state by Leonid Brezhnev . In the 1970s, there was a brief détente of relations with the United States, but tensions resumed with the Soviet--Afghan War in 1979 . In the mid-1980s, the last Soviet leader, Mikhail Gorbachev, sought to reform and liberalize the economy through his policies of glasnost and perestroika . Under Gorbachev, the role of the Communist Party in governing the state was removed from the constitution, causing a surge of severe political instability to set in . The Cold War ended during his tenure, and in 1989, Soviet satellite states in Eastern Europe overthrew their respective communist governments . </P> <P> With the rise of strong nationalist and separatist movements inside the union republics, Gorbachev tried to avert a dissolution of the Soviet Union in the post-Cold War era . A March 1991 referendum, boycotted by some republics, resulted in a majority of participating citizens voting in favor of preserving the union as a renewed federation . Gorbachev's power was greatly diminished after Russian President Boris Yeltsin played a high - profile role in facing down an abortive August 1991 coup d'état attempted by Communist Party hardliners . On 25 December 1991, Gorbachev resigned and the remaining twelve constituent republics emerged as independent post-Soviet states . The Russian Federation--formerly the Russian SFSR--assumed the Soviet Union's rights and obligations and is recognized as the successor state of the Soviet Union . In summing up the international ramifications of these events, Vladislav Zubok stated: "The collapse of the Soviet empire was an event of epochal geopolitical, military, ideological and economic significance ." </P> <Table> <Tr> <Th> Part of a series on the </Th> </Tr> <Tr> <Th> History of Russia </Th> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> <Table> <Tr> <Td> Early Slavs / Rus' </Td> <Td> pre-9th century </Td> </Tr> <Tr> <Td> Khazar Khaganate </Td> <Td> 7th--10th century </Td> </Tr> <Tr> <Td> Rus' Khaganate </Td> <Td> 9th century </Td> </Tr> <Tr> <Td> Volga Bulgaria </Td> <Td> 9th--13th century </Td> </Tr> <Tr> <Td> Kievan Rus' </Td> <Td> 882--1240 </Td> </Tr> <Tr> <Td> Vladimir - Suzdal </Td> <Td> 1157--1331 </Td> </Tr> <Tr> <Td> Novgorod Republic </Td> <Td> 1136--1478 </Td> </Tr> <Tr> <Td> Mongol Yoke </Td> <Td> 1240s--1480 </Td> </Tr> <Tr> <Td> Grand Duchy of Moscow </Td> <Td> 1283--1547 </Td> </Tr> <Tr> <Td> Tsardom of Russia </Td> <Td> 1547--1721 </Td> </Tr> <Tr> <Td> Russian Empire </Td> <Td> 1721--1917 </Td> </Tr> <Tr> <Td> Russian Republic </Td> <Td> 1917 </Td> </Tr> <Tr> <Td> Russian SFSR </Td> <Td> 1917--1922 </Td> </Tr> <Tr> <Td> Soviet Union </Td> <Td> 1922--1991 </Td> </Tr> <Tr> <Td> Russian Federation </Td> <Td> 1991--present </Td> </Tr> </Table> </Td> </Tr> <Tr> <Td> Timeline </Td> </Tr> <Tr> <Td> Russia portal </Td> </Tr> <Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> </Table>

When did the ussr change its name to russia