Every one of these crises could have resulted in a global conflagration. Earlier crises (such as the Berlin Blockade of 1948 or the Korean attack of 1950) could have led to war, but they took place before the superpowers developed huge stockpiles of nuclear-armed intercontinental missiles. Each crisis was eventually resolved in favor of peace, but in every case both sides relied on gambles, and survived as much by luck as by strategy.

An international “crisis” is the anxious space between peace and war. It is defined by three things: time, threat, and the likelihood of violence. The shorter the time, the greater the sense of threat to important interests, and the greater the chance of physical harm, the more intense the crisis. By definition, it cannot go on indefinitely: like the analogous medical term, it’s the point at which things must get better or worse. The July crisis of 1914 lasted only weeks, for example, but plunged the Great Powers into their first global war.

During the Cold War, “crisis” had a special connotation, because each moment of political conflict raised the possibility of nuclear war between the United States and the Soviet Union. Every confrontation carried the potential not only for war, but for the extermination of human civilization. While we look back on these periods now as something like curios in a museum, they were moments of existential fear for both American and Soviet leaders.

At least those days are over. Or maybe not: at this moment, Russian forces under the command of President Vladimir Putin are poised on the border of Ukraine. If they begin to move west, time, threat, and interest will collide once again. Europe, and the world, will be plunged into a real crisis, the likes of which we have not seen since the Cold War. Before the next crisis begins, it might worth reviewing the five worst crises of the Cold War before we find ourselves once more playing for time in the face of war.

1. The Wall and the Diplomat: Berlin, 1961

“When I go to sleep at night,” Secretary of State Dean Rusk said in 1961, “I try not to think about Berlin.” The Western garrisons in the divided capital of Germany were, for the duration of the Cold War, the West’s exposed nerve, symbols of resolve in the middle of the now-deceased ersatz East German “republic.” In October 1961, a few months after the Berlin Wall went up, an American diplomat tried to cross through “Checkpoint Charlie” into East Berlin. The East German police – whose authority the United States did not recognize – demanded papers. The diplomat refused, and later came back with jeeps and soldiers. Again, the local cops demanded he accede to their demands.

This time, the Americans sent tanks. The Soviets, having been alerted to the situation, also sent tanks of their own. For three days, the U.S. and the USSR stared down each other’s gun barrels on a German street. Finally, the Americans quietly proposed that the Soviets test the waters by pulling back one tank. They did so, and the Americans reciprocated. The crisis was over, but West Berlin remained until 1989 a Western outpost in the midst of the Communist camp.

2. The Closest Call: Cuba 1962

The history of the Cuban crisis is well known and need not be retold here. As in Berlin a year earlier, John F. Kennedy faced Soviet leader Nikita Khrushchev, and once again the superpowers were “eyeball to eyeball.” Khrushchev had miscalculated badly; he wanted to gain a quick strategic advantage not only over Kennedy, but over his own military, who objected to his notion that missiles could replace men. Although Kennedy agreed to a secret deal to remove similar U.S. missiles from Turkey, Khrushchev was humiliated, and Cuba was used against him when he was deposed by his Kremlin colleagues two years later.

Had the Americans proceeded with plans to bomb the Cuban missile sites, it would almost certainly have meant nuclear war. Even an accident or a moment of panic could have cascaded into disaster, especially if an itchy trigger finger on either side produced a naval conflict around the quarantined island.

One interesting note: beloved leftist icon Fidel Castro encouraged the Soviets to strike first with nuclear weapons if Cuba were invaded. Khrushchev upbraided Castro, and the Cuban dictator eventually regretted his recommendation to start World War III – albeit fifty years later.

3. The War the Soviet Generals Wanted: Vietnam, 1965

In November 1965, Lyndon Johnson reportedly exploded with rage at a meeting with the Joint Chiefs, who wanted him to go bigger in the newly launched intervention in Vietnam. Johnson swore a blue streak at them for being willing, in his view, to risk nuclear war over Vietnam. As it turns out, Johnson wasn’t the only one having a problem with generals.

After the Soviet collapse, previously censored memoirs of a Khrushchev political ally, Anastas Mikoyan, were finally published in Russia. Mikoyan related a chilling story, also from 1965: the Soviet General Staff, incensed by the U.S. bombing of Vietnam and earlier U.S. action in the Dominican Republic, suggested increasing pressure on...yes, Berlin:

[The Soviet Minister of Defense, General Rodion Malinovskii] asserted that we should not be limited by anything we were already doing to help Vietnam, and that after the Dominican events we should expect action directed against Cuba. Thus we should actively counter the Americans. It was proposed that in the West (that is, in Berlin and on the border with Western Europe) a military demonstration should be carried out, and to send certain units--airborne forces and others--from our territory to Germany and to Hungary. He emphasized that we must be ready to strike West Berlin. Later, he added his own comment that “in general, in connection with the emerging situation, it follows that we do not fear approaching the risk of war.”

Mikoyan wrote that the military’s position “staggered” him, and Soviet civilian leaders, aghast, squashed the idea quickly. With both sides looking to make Vietnam a larger fight, however, it’s lucky that the spring of 1965 didn’t turn out to be a lot hotter than it already was.

 4. Red Alert: The Middle East, 1973

After a punishing defeat in the Arab-Israeli 1967 Six-Day War, the Egyptians were looking to get even.  In 1973, Egypt – at that point a Soviet client state and the lynchpin of the Soviet position in the Middle East – executed a surprise attack on Israel at the outset of the Yom Kippur War.

Although the Egyptians and their allies achieved significant gains, the Israelis recovered sufficiently to counterattack, eventually surrounding and threatening to destroy the entire Egyptian Third Army. As U.S. Secretary of State Henry Kissinger tried to hold back the Israelis, the Kremlin tried to save its Egyptian friends with the novel solution of a joint U.S. – Soviet military intervention to separate the warring parties.

The Americans instantly recognized the Kremlin’s offer for what it was: an attempt to introduce Soviet troops into the Middle East. Washington refused. The Soviet leadership then threatened to intervene unilaterally, sending President Richard Nixon a message that Kissinger later characterized as one of the most serious challenges to a White House ever sent from Moscow.

Nixon in late 1973 was weakened by the storms of scandal and less than a year from resigning, which may have prompted the aggressive Soviet move. Kissinger and the White House team, however, responded by bringing the U.S. military – including America’s strategic nuclear forces – to a higher alert status. It’s possible that the Soviets were bluffing; a former Soviet advisor has since denied there were any Soviet invasion plans afoot.  Serious or not, the Soviets dropped the idea, and a few weeks later, the Americans quietly stood down their alert.

If Soviet forces had gone into the region and ended up in a shooting war with the Israelis, things would have been very different – to say nothing of what could have happened had Israeli leader Golda Meir not prohibited the option of using the Israeli nuclear arsenal itself.

5. This is Only an Exercise: Europe, 1983

The last major alert of the Cold War happened by accident, and the public didn’t know about it for decades. For that matter, neither did most of America’s NATO allies, even though they were involved.

In 1983, relations between the United States and the Soviet Union were as cold as they had ever been, with President Ronald Reagan’s administration pushing a tough policy of confrontation and Soviet boss Yuri Andropov (a hardline former head of the KGB) leading a coterie of increasingly paranoid old men in the Kremlin. It was a tense year, from Reagan’s “evil empire” speech in March to the Soviet downing of a civilian airliner in September.

In November 1983, the United States and NATO conducted an exercise, code-named “ABLE ARCHER.” This was a war game designed, among other things, to test channels of communication between North America and Europe during the transition from conventional to nuclear operations in a hypothetical World War III. Although NATO’s traffic was encoded, every message began with “Exercise,” which U.S. and NATO leaders assumed the Soviets could recognize.