The Cold War, a hostile rivalry between the United States and the Soviet Union, lasted from the late 1940s until the collapse of the Soviet Union in 1991. The war was "cold" only in that the U.S. and the USSR never fought each other in a direct military confrontation. They never used their stockpiles of nukes. 

But both superpowers absolutely threatened annihilation with their stockpiles of nukes. 

Instead of your usual battles, these two bozo-countries participated in "proxy wars" by supporting allied nations in numerous "hot" wars—like Korea, Vietnam, and Angola—and playing lots of head games. 

They boycotted each other's Olympic Games, challenged each other to an arms race and a Space Race, and held international thumb-war tournaments. 

Well, maybe not that last one. But they may as well have thrown that in there, too.

The Cold War defined both countries' foreign policies through the second half of the 20th century. Both Americans and Soviets competed for allies to maintain and widen their respective spheres of influence around the world and each side viewed the Cold War as a battle between civilizations. 

In the worldwide clash between American capitalism and Soviet communism, only one could prevail.

Or so they seemed to think.

For more than 40 years, the Soviet-American conflict hung heavy over global affairs, shaping the world with massive military buildups, a never-ending nuclear arms race, intensive espionage, and fierce technological competition as each side tried to gain the upper hand in preparation for the thermonuclear "hot war" all humans feared would someday come.

The joyous victory celebrations that marked the end of World War II had barely ended before that war's greatest victors—the United States and Soviet Union—found themselves locked in a terrifying new conflict.

• How did one-time allies turn so quickly into mortal enemies?
• What would happen if the Soviet-American "Cold War" turned hot?
• Could human civilization survive a clash of superpowers in an age of nuclear weapons?

These were the questions that haunted American life in the second half of the twentieth century, as the Cold War shaped every aspect of American society—its politics, its military and diplomacy, its education system, its culture, even its highway system.

We now know, of course, that despite occasional flare-ups, the Cold War never escalated into an apocalyptic World War III. The decades-long standoff between American capitalists and Soviet communists ended peacefully, with the sudden dismantling, from within, of the Soviet empire after 1989.

America prevailed.

But just because the long conflict ended happily doesn't mean it should soon be forgotten. The lessons learned while staving off nuclear holocaust during the Cold War may yet prove vital to the survival of humanity on this planet.