Fifty years ago, the world was on the brink of Armageddon.

The Russians had secretly installed nuclear missiles in Cuba, aiming them at Washington and other American cities. Confronting the Soviet Union at the United Nations, the United States displayed photographic evidence and demanded the missiles be removed. On Oct. 22, 1962, President John F. Kennedy ordered the Navy to blockade Cuba. Six days later Soviet Premier Nikita S. Khrushchev ordered the missiles dismantled.

How did that crisis develop? What lessons were learned that might be applied in these still-perilous times? The first lesson actually stems from Kennedy’s first meeting with Khrushchev in Vienna. Recently elected, Kennedy, 45, was young, dashing and charismatic. Khrushchev, 68, was a committed Communist who had been trained by Stalin, one of history’s most brutal tyrants. Sometime during the meeting Khrushchev concluded Kennedy was a light-weight and could be pushed around.

Lesson 1: The perception of power and a willingness to use it establishes the base of international relations. To be perceived as weak, is to invite confrontation.

Two years later Khrushchev made his nuclear gamble, but by the end of the Missile Crisis he knew his bluffs were no match for strategically superior American technology and power. The evidence Kennedy had could only have been obtained by over-flights, and the U.S. military was clearly ready to deal with the threat. Thus . . .

Lesson 2: Peace is attained and maintained by strength, not by weakness.

In his memoirs Khrushchev recounts how Fidel Castro urged him to initiate a nuclear attack. Despite his visceral anti-Americanism, Castro realized later that he was only a pawn in the Cold War chess game. He had also learned how far he could push his anti-American agenda. Later he would send tanks to the Golan Heights to assist Syrians fight Israel, deploy the Cuban army under Soviet command in Africa, facilitate the flow of drugs into the United States, order civilian American aircraft shot down in international airspace over the Florida Straits, and ally Cuba with the likes of North Korea, Syria and Iran. But since the 1962 crisis, he has not put Havana in a situation that jeopardized millions of American lives. What he learned and the world should have learned is . . .

Lesson 3: The United States won’t tolerate a nuclear gamble.

Seemingly, it has never bothered Fidel Castro or his brother Raúl, then minister of the armed forces, that millions of Cubans could have been killed. Fidel still rallies Cubans with the slogan: “ Morir, antes que retroceder,” or “Die before stepping back.” The Castros don’t admit their jig is up, communism has failed or that their regime won’t survive. To them every day in power is a victory. That “victory” is maintained only by the suffering and misery of the Cuban majority and sends quite another message to the world.

Lesson 4: Avoid complicity with governments whose whims supersede its people’s best interests and compromise their survival.

Bolstered by alliances with North Korea, Syria and Iran, the Castros’ dictatorship can still wreak harm and havoc. In recent months hundreds of peaceful advocates demonstrating for change have been imprisoned. So too, has American aid worker Allan Gross, who’s serving a 15-year sentence for delivering a laptop computer and satellite telephone to a Jewish community. Nonetheless, President Obama — in a gesture of friendship — lifted U.S. restrictions on the amount of money Americans can send to Cuban relatives. He also urged the Cuban government to lift the punitive taxes it imposes on remittances. The Castros ignored the entreaty. To those in Washington still urging the United States to lift all remaining sanctions with no quid pro quo, the next lesson ought to be obvious.

Lesson 5: Unilateral concessions don’t advance American interests in instilling a rule of law in Cuba, re-introducing a market economy, or improving the lot of the Cuban people.

The1962 Missile Crisis was the apex of the Cold War. Much of the world has since changed. Cuba has not. Until the Castro brothers set aside their Cold War hatreds, and grant Cubans the human rights taken for granted by millions around the world, it is difficult to see how relations can change to the benefit of both nations. An old Spanish adage, “ No hay enemigo pequeño,” dictates:

Lesson 6: “There is no small enemy.”

It may also be the most important lesson.

Jeb Bush is the former governor of Florida. Frank Calzon is executive director of the Center for a Free Cuba in Washington, D.C.