My pilgrimage to the World War II beaches of Normandy was a reminder to me of what the United States meant to the world not that long ago -- and the troubling contrast with today.
Before heading to Omaha Beach -- the iconic heart of D-Day heroism -- I spent several hours at Caen's World War II museum where you literally descend down an inclined walkway into the murderous madness that engulfed Europe in the 1930s.
It is still hard to imagine that a racist fanatic like Adolf Hitler could gain control of Germany, then one of the world's most advanced civilizations, and that he could win over enough Germans to undertake various forms of mechanized slaughter.
There was, of course, a long history in Europe of such butchery, from the Roman conquests more than two millennia ago, through the Christian religious wars of the middle of the last millennium to the wholesale killing of World War I.
Indeed, that European tendency to periodically sink into bloody barbarism was the historical backdrop of the American Revolution.
In creating a new Republic, the Founders tried to inoculate the United States from some of those viruses -- prohibiting a national religion, restraining the Executive's war-making powers and cautioning against entangling alliances.
But the more integrated world of the 20th Century made isolationism a difficult approach.
By the 1930s, Europe had gotten itself into another fix with global implications. The German business elite had decided that Hitler was the man who could stop the rise of Bolshevism and regain some of Germany's lost pride and territories from World War I.
Great Britain and France made some appeasing gestures toward Hitler by restoring land that had been stripped from Germany, but that only encouraged Hitler's megalomania.
Soon, Hitler's aggression against Poland pushed matters too far, shoving Europe into yet another war. France soon fell to Germany's military might and Great Britain struggled under an unprecedented aerial bombardment focused on civilian targets.
Quietly assisted by President Franklin Roosevelt, Great Britain withstood the air campaign, causing Hitler to turn his attention to the Soviet Union.
Meanwhile, half a world away, Germany's fascist allies in Japan were expanding their own empire and chafing against American power in the Pacific. After Japan's surprise attack on Pearl Harbor, the United States entered the war against Japan and its Axis allies.
As the war expanded, so did the carnage, both involving armies and civilians.
Under the cover of war, Hitler advanced his genocidal goal of exterminating European Jews, whom he used as scapegoats for Germany's troubles. The Nazis' use of roving execution squads gave way to the construction of industrial-style killing factories.
The future of humanity looked exceedingly bleak.