The late-night stopover in Kyiv in January 1994 was a last-minute addition to Bill Clinton’s itinerary for his first European trip as president. The brief swoop-down at the airport was a reward to Ukrainian President Leonid Kravchuk for agreeing to surrender the 1,800 nuclear warheads that his nation inherited from the 1991 breakup of the Soviet Union.

It’s funny the little things you recall from a hinge-of-history moment like this.

The belching buses that carried the traveling reporters from the press charter to the terminal were so ancient that it was easy to imagine them transporting Joe Stalin’s political prisoners to their inevitable fate.

The terminal at Boryspil International Airport was unheated, adding a wintry note to the meeting between Clinton and Kravchuk, a survivor from the Soviet era when he headed the propaganda ministry in Ukraine.

Even though it was around midnight when the private negotiations were over, the Ukrainians insisted for protocol’s sake on a formal banquet in the frigid terminal that no one wanted to eat.

Mostly what I remember, though, is the heady optimism of the mid-1990s.

The Soviet Union had collapsed under the weight of its own internal contradictions. Boris Yeltsin — the symbol of citizen resistance to an attempted 1991 coup by hard-line Communists — was now the president of a democratic Russia.

Freed from Soviet dominance, the Czechs, the Poles and the Hungarians had embraced Europe and were eager to bask in the security provided by NATO membership.

The United States was unchallenged as the only surviving global superpower. And the seeming triumph of American values — particularly democracy and free markets — symbolized the shining 21st century ahead.

If only.

Now every morning brings with it the alarming question: Is today the day that the Russian invasion of Ukraine will begin? Or will the fragile veneer of peace last another 24 hours?

In a sense, the chilling uncertainty is reminiscent of the days leading up to the Nazi invasion of Poland on Sept. 1, 1939. Everyone knew that war was coming — the only question was when.

(A wondrous historical detail: 22-year-old John Kennedy arrived in Berlin in mid-August 1939 as part of his seven-month European Grand Tour. When JFK left to return to London, where his father was ambassador, he carried with him an accurate warning from a top U.S. diplomat that the Nazis would march within a week.)

It is tempting to look back at the Clinton era and concede the missteps that seem obvious in hindsight.

The rapid expansion of NATO to the borders of the former Soviet Union fueled Russian paranoia and ultimately the resentment of the weakness of the Yeltsin years.

In their enthusiastic advocacy of the privatization of former Soviet companies, American economic advisers abetted the rise of Russian oligarchs.

Idealism also fostered the naive belief that elections alone would be a guarantee of perpetual democracy. From Viktor Orban in Hungary to Putin himself, it is tragic to see how easily the forms of democracy can be adapted to one-party autocracy.

What was not a mistake was the denuclearization of Ukraine, Belarus and other former Soviet republics. The risk of black-market nukes in an age of terrorism is too great to have ever entrusted these weapons to fledgling states without well-developed command-and-control mechanisms.

Yes, Russia’s vast arsenal gives Putin a freedom to threaten — and potentially invade — that is not granted to non-nuclear states. But that freedom to menace has existed since the 1950s. It is why Dwight Eisenhower did nothing when the Hungarians battled Soviet tanks in 1956 and why America passively stood by as the Prague Spring of 1968 was crushed.

The hardest thing for many Americans to acknowledge is that so much of what happens in the world isn’t about us.

It is difficult, for example, to see how Putin’s behavior has been influenced by the tattered American withdrawal from Afghanistan. Especially since Afghanistan is not exactly a shimmering symbol of Russian military might.

But if Putin were to invade, Republican talking points and TV ads would angrily blame the supposed weakness of President Joe Biden and the Democrats. That would be nonsense unless the GOP believes that former President Donald Trump, that Putin sycophant, would have sent American troops to Ukraine to thwart an invasion.

Politics still stops at the water’s edge, but that’s because Americans don’t care about foreign policy unless U.S. troops are under fire. Voters would probably barely notice if Biden’s threats of sanctions helped convince Putin to take an off-ramp and slowly withdraw his troops from Ukraine’s borders.

It is possible that the threat of enhanced economic sanctions by America and our European allies might end up deterring Putin. That said, whatever the slow-moving Congress does on its own Russian sanctions will probably have about as much effect as putting an angry message in a bottle and dropping it in the Black Sea.

Even if war is averted, Biden sometime soon has an obligation to better explain what the United States can — and cannot — be expected to do if Russia and China threaten global borders.

Taiwan, which has loosely been under the American security umbrella since China fell to the Communists in 1949, is the true test of Biden’s resolve. In an October CNN town meeting, Biden acknowledged that America would come to Taiwan’s defense in the face of Chinese attack.

That isn’t official U.S. policy and Biden aides tried to walk back the president’s comments. But strategic ambiguity can only take you so far. And even more than Ukraine, Taiwan is potentially at the center of Biden’s foreign policy.

These are difficult times for democracy and human rights. But the cause is a righteous one, even if sometimes global realities limit how much America can do in a crisis.