On November 7, 1917, Bolshevik forces led by the Marxist ideologue Vladimir Lenin and his compatriots Leon Trotsky and Joseph Stalin, seized power in the Russian capital, Petrograd. What followed was a protracted and bloody Russian civil war that ended in 1921 with the victory of the Bolshevik Red Army.

The Red Army not only took Russia, but was also victorious in satellite states like Ukraine, Belarus and the Caucuses that were previously part of the Russian Empire. Under czarist rule, non-Russian people were systematically oppressed, but Lenin promised change with the formation of the Union of Soviet Socialist Republics on December 30, 1922.

“Lenin worked out a system that would create a new kind of state—a federation in which each nationality would have their own cultural and territorial autonomy,” says Ronald Suny, a history professor and author of The Soviet Experiment: Russia, the USSR and the Successor States. “This was a very unique structure, this Union of Soviet Socialist Republics.”

The USSR was also the first state in the world built on Marxist-socialist principles of a collective economy and classless society. To the oppressed and colonized peoples of Africa and Asia, Lenin presented the USSR as an alternative political model that was radically democratic, anti-imperialist and egalitarian.

But the high ideals upon which the USSR was founded quickly eroded in the face of dire economic conditions and international isolation. Even before Lenin’s death in 1924, the Socialist revolution shifted away from workers’ rights toward rapid industrialization, forced collectivization and economic growth at any cost.

This poster from 1923 is entitled “Long Live the 1st of May,” a day celebrated by Socialists since the late 19th century. The USSR circulated propagandist artwork like this to promote the ideal of the new Soviet state as a worker’s paradise of peace, equality and prosperity.

During the brutal purges of Joseph Stalin in the 1930s, millions of Soviet citizens were branded as “enemies,” arrested by the secret police and shipped off to Siberian gulags.

“In the course of just one year, 1937 to 1938, Stalin executed nearly 700,000 of his own people,” says Suny. “Elites, industrial bosses, cultural figures—anyone he saw as the opposition.” Even close comrades were literally erased from Soviet history. Nikolai Yezhov, former head of the secret police, was executed by Stalin and then deleted from this altered photo.

The Ukrainian famine of the early 1930s was a man-made punishment for daring to stand up to Stalin. When Ukrainian peasants resisted mass resettlement to collective, state-run farms, Stalin decided to starve them into submission. An estimated 3.9 million Ukrainians died after Soviet forces confiscated Ukrainian grain harvests.

This photo recorded the Soviet Union’s first successful detonation of a nuclear weapon on August 29, 1949. The 20-kiloton atomic bomb, nicknamed “First Lightning,” was built using American technology leaked to the Soviets by the German-born atomic physicist and convicted spy, Klaus Fuchs. The Soviet achievement launched a Cold War nuclear arms race resulting in each side amassing more than 10,000 warheads.

After World War II, Stalin ordered the construction of massive skyscrapers in Moscow to prove that the USSR was as wealthy and powerful as the West. "They go to America and they gasp, 'Ah, what huge buildings!'” Stalin reportedly said. “Let them now go to Moscow, see what kind of buildings we have, and let them gasp."

Shown here are the Gothic-spired towers of Moscow State University, one of the “Seven Sisters” that epitomize Stalinist architecture in all of its stark grandeur.

In the 1950s, the Cold War arms race expanded into a Space Race for technological superiority. The Soviet Union took the lead on October 4, 1957 with the launch of Sputnik 1, the first manmade object to orbit the Earth. Next, the Soviets undertook a series of experiments with animals aboard the orbiters to test the feasibility of sending humans to space.

One unlucky dog, Laika, became the first animal to travel into space when she was launched aboard the Sputnik 2 spacecraft. Laika, a part-Siberian husky who had lived as a stray on the Moscow streets before being used in the Soviet space program, died within hours from overheating and panic.

The USSR also put the first man in space in 1961 with the launch of a 27-year-old test pilot Yuri Alekseyevich Gagarin. Gagarin circled Earth once in a Vostok spacecraft before ejecting 23,000 feet above the planet and parachuting safely down. The United States then beat the Soviets to the moon in 1969 with the landing of Apollo 11.

After Stalin’s death in 1953, Nikita Khrushchev instituted a policy of “de-Stalinization,” says Suny, dismantling the gulags, reining in the secret police and giving more autonomy to the Soviet republics.

But Cold War tensions continued to mount. One of the most famous flare-ups was the impromptu “kitchen debate” between Khrushchev and Vice President Richard Nixon during a tour of a cultural exhibition in Moscow.

This public lip-lock between the Soviet Union’s Leonid Brezhnev and East Germany’s Erich Honecker in 1979 commemorated the 30th anniversary of the alliance between the Communist states. The “socialist fraternal kiss” was embraced by Soviet leaders as the ultimate sign of Communist party loyalty.

On April 26, 1986, the Chernobyl nuclear power plant in Ukraine suffered a catastrophic explosion and fire, releasing more than 400 times the radiation of the atomic bomb that struck Hiroshima.

Dozens of emergency responders died from acute radiation poisoning, and thousands more in the area contracted cancers from long-term exposure. The Soviet government tried to cover up the extent of the disaster, but the disaster struck a devastating blow to national pride.

When Mikhail Gorbachev came to power in 1985, he introduced a series of striking reforms that shook up 60 years of Soviet policies. Known in Russian as perestroika and glasnost (“restructuring” and “openness”), Gorbachev’s reforms were intended to end political repression, democratize Soviet elections, and jumpstart the faltering Soviet economy.

Gorbachev also pulled the Soviet Union out of its disastrous war in Afghanistan and signed the first nuclear disarmament treaty with President Ronald Reagan, a vocal anti-Communist.

Among Gorbachev’s reforms was to loosen Soviet rule over non-Russian nations that had been part of the Soviet Bloc. This created an independent, democratic momentum that led to the collapse of the Berlin Wall in November 1989, and then the overthrow of Communist rule throughout Eastern Europe. Gorbachev also introduced an initiative to grant more autonomy to the USSR's constituent republics.

“You can say the Soviet Union ultimately committed suicide by weakening the center,” says Suny. Angered by Gorbachev’s policies, a group of hardliners staged a failed military coup in 1991. Boris Yeltsin, pictured atop one of the stalled tanks, emerged as a popular leader, prompting Gorbachev’s resignation.

On December 25, 1991, the Soviet hammer and sickle flag was lowered for the final time over the Kremlin, thereafter replaced by the Russian tricolor flag. The USSR dissolved into 15 independent countries: Armenia, Azerbaijan, Belarus, Estonia, Georgia, Kazakhstan, Kyrgyzstan, Latvia, Lithuania, Moldova, Russia, Tajikistan, Turkmenistan, Ukraine and Uzbekistan.