The Soviet Union was established in the aftermath of the Russian Civil War, when Bolshevik forces reconquered most of the former Russian Empire. Under the leadership of Joseph Stalin, it rapidly industrialized, although the Great Purges hampered progress. At the beginning of World War II, the Molotov-Ribbentrop Pact came into effect, and the Soviet Union took half of Poland.
In late 1939, the Soviets launched a war against Finland, intending to reclaim territory lost during the Revolution. However, they met stiff resistance and sustained heavy casualties. The war ended with minimal Soviet gains.
On June 22, 1941, Germany launched Operation Barbarossa, the largest military operation in human history. Hundreds of thousands of German soldiers poured across the ill-defended Soviet border. Soviet troops took massive casualties and retreated across the steppes. By winter, the Siege of Leningrad had begun, the Battle of Stalingrad was raging, and German forces were nearly at Moscow.
In 1942, the tides began to turn. The Battle of Stalingrad claimed several hundred thousand lives on both sides. Although at times the Germans controlled up to 90% of the city, Soviet reinforcements managed to outflank and captured nearly 90,000 troops of the German Ninth Army. The brutal winter weather also took its toll on the Germany army.
In 1943, a salient around the city of Kursk became the site of the largest battle in human history. The Battle of Kursk involved thousands of tanks and aircraft on each side. The Germans were heavily defeated and forced to turn back.
In 1944, the Soviet Operation Bagration retook most of Belarus and brought the front line back to where it was pre-war. The Soviets took Warsaw immediately after the Warsaw Uprising, and liberated most of the concentration camps in Poland.
In August, the Soviet Union declared war on Japan, and quickly took over Manchuria. On September 2, 1945, partly due to this and partly due to the atomic bombings of Hiroshima and Nagasaki, Japan surrendered.
After World War II, the Soviets entered the Cold War against the United States. In 1949, they tested their first atomic bomb, known as Joe-1. In 1950, they provided support to the North Koreans in the Korean War.
The Space Race began in 1959, when the Soviet Union launched the world's first satellite, Sputnik. The Soviets also put the first man in space, Yuri Gagarin, and the first woman. However, in 1969 the United States beat them to moon.
The Cuban Missile Crisis in 1962 was perhaps the closest the world came to nuclear war. The Soviet Union, under Nikita Khrushchev, began stationing nuclear missiles on Cuba, only away from the United States. The American President, John F. Kennedy, began a blockade of Cuba. At the last minute, Khrushchev backed off, and the missiles were dismantled.
In the 1980s, the Soviet Union began to falter. The Soviet war in Afghanistan drained resources and was unpopular at home, and a series of weak leaders were unable to revitalize the union. When Mikhail Gorbachev took power in 1985, he instituted widespread reforms of glasnost and perestroika. Instead of easing tensions, these encouraged nationalist attitudes in the Baltic states and the Caucasus.
In 1990, constituent republics began to secede from the union. Gorbachev refused to stop them, and by 1991 the union had fallen apart. The Commonwealth of Independent States was established, and the Russian Federation succeeded the Soviet Union.