America has endured many catastrophic events since the end of the Second World War, 75 years ago. Hurricanes, floods and fires. Assassinations and 9/11. Wars, both Cold and hot.

But the Virus, as we may eventually call it, is different. While it is still in its early stages, and none of us knows how this chapter in our history will end, it isn’t hard to see that it may become our closest equivalent to “the War” and the Great Depression, each of which was, in its time, an existential threat to the country.

Already, we know, that this is something that we will remember  for the rest of our lives as a defining moment in our lives and the country’s history.

What raises a threat like this to the level of an existential threat is the presence of these characteristics, all of which are present today: It is deeply destabilizing and unnerving. It presents challenges that we haven’t seen before and have no prepared response to. It involves every American, directly. And it is not possible to see how or when it will end.

Franklin Delano Roosevelt, whose presidency bridged the Depression and the War, understood that the greatest danger to any society faced with an existential threat was panic. “The only thing we have to fear,” he famously said, in his first inaugural address, “is fear itself.”

When we were swept into the War, in 1941, Roosevelt also understood that people need stable and strong leadership, reassurance, confidence and hope. The day after the attacks on Hawaii, Roosevelt stirred a shocked and angry nation with his speech to Congress and the nation, in which he said, “No matter how long it may take us to overcome this premeditated invasion, the American people in their righteous might will win through to absolute victory.”

The people who endured the Depression and the War – our parents, grandparents and great-grandparents – have some things to share with us about fear and determination and unity. They know something, first hand, about what we’re experiencing today, and about not knowing where the bottom is, or how this story will end.

We know that the Depression finally ended with the onset of the War, and that the American economy continued to grow for decades thereafter. But they didn’t.

We know the War ended with Hitler dead in a bunker in Berlin, and Japan’s emperor surrendering. But Americans, until late in the War, didn’t know if or when we would win.

The people who lived through those experiences were gripped with the same kind of fear that many of us feel now. Was this the new order of things, they must have wondered? Is this the way the future will look? Will we, and our children, be able to survive in this new world? Is God still on our side?

What would the people of those times say to us, to help us get through this crisis? They’d say that this is a time for calm strength and determination, not hysteria and selfishness. They’d urge us to overcome our old divisions in favor of a new unity. And they would remind us that however dark the days ahead may seem, a new kind of national purpose can arise from these collective threats, as it did with theirs.

The Depression led directly to a renewed desire to care for each other, like Social Security and unemployment insurance. The War gave us a sense that we were truly a nation, of varied backgrounds and beliefs, to be sure, rather than a loose combination of states, regions, cultures, races and interests. That, in turn, led to national actions that ranged from giving veterans access to colleges and their own homes, an interstate highway system and progress on race relations, reducing poverty and cleaning our air and water.

Most of all, what the people of the Great Depression and World War II would say to us is this: Reject those who would exploit your differences and fears for their own gain, whether personal or political. Turn instead, they would say, to each other.