On Christmas night, 1991, Soviet premier Mikhail Gorbachev resigned and relinquished his powers, including the nuclear codes, to Russian President Boris Yeltsin. The flag of the USSR that flew over the Kremlin was lowered, never to be raised again.

The next day, the Soviet legislature formally dissolved the Soviet Union, bringing a final end to the Cold War.

In a Christmas address from the Oval Office, then-President George H.W. Bush called the Communist regime’s collapse “one of the greatest dramas of the 20th century” and “a victory for democracy and freedom.”

“30 years ago today, the Soviet Union dissolved and the Cold War ended. Few people under 40 will appreciate what a cataclysmic event this was. The Cold War (and threat of nuclear war) had dominated our politics for 45 years, and the Soviets just giving up was inconceivable,” Manhattan Institute Senior Fellow Brian Reidl tweeted Saturday.

This landmark anniversary comes as the threat of Russian aggression in Eastern Europe looms once again. “The breakup of the Soviet Union was the collapse of a historic Russia … We became a different country. What had been built over a millennium was lost to a large extent,” President Vladimir Putin said earlier this month, POLITICO reports.

Tens of thousands of Russian troops are currently massed on the border of former Soviet satellite Ukraine, and intelligence experts warn that an invasion could occur in the next few weeks.