1991: the fall of the Soviet Union: when America's Cold War adversary collapsed 20 years ago, it freed millions from oppression and left the U.S. as the world's only superpower.

• Author: Wines, Michael
• Position: TIMES PAST

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The Soviet Union was a colossus that covered one sixth of the Earth's land and held sway over even more. It kept a third of Europe captive, and blocked escape with troops, tanks, and concrete walls. In its Cold War battle with the U.S. starting in 1945, it edged the world so close to destruction that cities across America built bomb shelters and schools taught nuclear-blast survival alongside algebra and history.

Then, on Christmas Day 1991, the Union of Soviet Socialist Republics (U.S.S.R.)--15 states lashed together for almost 75 years into one of history's grandest and most fearsome empires--dissolved, the victim of a dying economy and its own citizens' thirst for freedom.

The end came peacefully and with stark simplicity: "I hereby discontinue my activities at the post of president," its leader, Mikhail Gorbachev, declared. "We're now living in a new world."

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And a jubilant one--at least initially.

"You waved goodbye to everything you had been born with," recalls Dmitri Trenin, a Moscow scholar. "Everything around you--in political, social, and economic terms--was collapsing. And there was a promise of something new and better emerging."

The fall of the Soviet Union ended a 46-year struggle between two superpowers that threatened to destroy not only themselves, but also the rest of humanity through nuclear war.

"I would call it, after World War II, the most significant event of the 20th century," says Paul Hughes at the U.S. Institute of Peace in Washington. "It allowed millions of people to stop living in fear."

Soviet dictatorship started idealistically, with the theory that everyone should share society's wealth. Communism, its founding ideology, argues that privately owned businesses and industries should be confiscated and collectively owned by the state for everyone's benefit.

In 1917, Vladimir Lenin led the Russian Revolution, which toppled Tsar Nicholas II after World War I left the nation sapped and near starvation.

Lenin and his brutal successor, Joseph Stalin, remade the vast, mostly illiterate nation into an industrial giant, but at a staggering cost: At least 40 million people died from famine, persecution, and mass executions under Stalin.

"Not since the days of Peter the Great, who sought to westernize Russia by force, had the country witnessed so violent a transformation," The New York Times wrote about Stalin.

The Iron Curtain

During World War II, the Soviet Union repelled Hitler's army. After the war, it installed puppet governments in Eastern European nations captured from Germany, leading former British Prime Minister Winston Churchill to say that an "iron curtain" had descended across Europe. Soviet leaders declared themselves devoted to the West's destruction.

Thus began the Cold War--a standoff between Communism and capitalist Western nations led by the U.S.--that threatened global annihilation (see timeline, p. 20).

After the Soviet Union exploded an atomic bomb in 1949, the two sides began a frantic arms race, eventually building 70,000 nuclear bombs. American schools taught students to "duck and cover" under their desks if they saw a nuclear bomb's bright flash--and issued dog tags so their bodies could be identified.

"There was a real risk of things getting out of control and real miscalculations being made," says Fiona Hill, a Russia scholar at the Brookings

Michael Wines, now a correspondent in the Beijing bureau, was based in Moscow for The New York Times from 1998 to...