The 100-year anniversary of the most important event in the 20th century passed recently with predictably scant notice in the American media. The anniversary can’t be that of the allied D-Day invasion of Normandy during World War II, because that event happened only 70 years ago. And it’s not the anniversaries of the attack on Pearl Harbor, the moon shot, or the 9/11 attacks.

On June 28, 1914, one hundred years ago, the Archduke Ferdinand—to be the future ruler of the Austro-Hungarian Empire—was gunned down by a Serbian-government sponsored assassination team. What? A few Americans might vaguely remember this incident from their high school social studies or history classes, but is it the most important event in the 20th century? Yes.

The event was the spark that triggered what is now called World War I but really should be called, “The World War: Part I.” The more recent and popular World War II should be called, “The World War: Part II,” because the results of World War I caused World War II. Thus, World War I was historically much more important than its more heralded successor.

Of course, World War II is more popular because we have its veterans still living, because the villains vanquished were more evil than those in the First World War, and because the United States sat unrivaled as a world power after its victory in the second war. Thus, the bipartisan foreign policy elite uses World War II to show that the United States must in stop any aggression overseas before it snowballs into a threat to the U.S. homeland. British Prime Minister Neville Chamberlain’s appeasement of Adolf Hitler at Munich in 1938, despite Hitler’s aggressive behavior in Czechoslovakia, is usually dragged out to demonstrate what not to do in foreign affairs and to illustrate that that the United States must deal very harshly with any such encroachment (for example, Vladimir Putin’s recent annexation of Russophilic Crimea). Even here, Chamberlain had no choice but to appease Hitler, because Britain was not yet ready for conflict and had to catch up with Hitler’s war preparations (including obtaining the air defenses that saved the British in the critical Battle of Britain).

As for the United States, if you ask any American why the Japanese bombed Pearl Harbor, you will usually get a blank stare instead of an analysis of American actions prior to the attack—the U.S. attempt to strangle the Japanese economy and military by cutting off petroleum-based exports (America was then the largest producer) in reaction to Japanese attempts to join the imperial club in East Asia, of which America and its allies were already members. Americans also conveniently forget that President Franklin Delano Roosevelt refused Japanese overtures to negotiate an end to the embargo and avoid war. FDR already had learned the false lesson of Munich that all negotiation to avoid war is appeasement.

But all this would not have happened if it hadn’t been for American involvement in World War I, which tipped the victory to the allied side and caused Britain and France to falsely declare the Germans guilty of starting the war, rub its nose in defeat with heavy war reparations, and grab German and its losing allies’ colonies overseas. Woodrow Wilson, the American president, also demanded that the German king, Kaiser Wilhelm II, abdicate. All of these post-war depredations paved the way for the rise of the hyper-nationalist and jingoistic Hitler.

In reality, France and Russia, with its rapid military build up prior to the outbreak of the First World War, probably behaved more aggressively than Germany did. But the winners of war write the history, and Germany’s behavior in World War I now seems more aggressive in light of the evil Hitler’s subsequent aggression in World War II, which Germany also lost.

Austria-Hungary, Germany’s ally prior to the First World War, understandably felt the need to respond to a Serbian government-backed assassination of its second highest ranking official—clearly an act of war. Germany backed an Austro-Hungarian ultimatum and war, thinking that the conflict could be contained on the Balkan Peninsula, as two prior conflicts were in the previous few years, because Russia would not enter the war on behalf of Serbia. That assumption proved to be wrong, because the French were pushing their ally Russia to turn a conflict in the Balkans into a general war in Europe to get Russian help against their old enemy Germany. Britain was aligned with France and Russia and also entered the fray.

Thus, if we go back farther in history, which Americans rarely do, we learn the opposite lesson from merely examining Munich 1938 and World War II. We learn that the post-World War II U.S. policy of hyper-interventionism into the affairs of other nations was not the traditional foreign policy of the nation’s founders or of the United States for most of its history. The stark unintended consequences of World War I reaffirmed the founders’ inclination to stay out of wars on the other side of the world (especially those in Europe), to avoid entangling alliances, and to be suspicious of large standing armies. Of course, we got all three during the post-World War II Cold War.

The roots of that Cold War can also be traced to World War I. The possibility of allied victory with the belated entry into the conflict of the United States—the greatest industrial power at the time—and Wilson’s and the allies’ promises of aid to the Russian Kerensky government to stay in the war were pivotal in keeping Russia in a quagmire unpopular with its people. The only Russian party advocating getting out of the war was the Bolshevik party. Vladimir Lenin even said that the only reason the Bolsheviks rose to power during the second Russian revolution was the Russian public’s exhaustion from the carnage of World War I. In addition, most Americans don’t know that during the ensuing Russian civil war, the U.S. and its wartime allies invaded Russia to help anti-Bolshevik forces and to keep Japan out of the Russian far east. The suspicion of the West by the Russian communists originated here.

If the United States had let Germany win World War I by an exhausting 15-round decision, rather helping to achieve its knockout, the boundaries of Europe would have been slightly adjusted, as they had during all previous European wars that the United States had stayed out of. The 20th century probably wouldn’t have been by far the bloodiest in world history, because World War II and the Cold War likely would not have occurred.

And World War I just keeps on giving in the 21st century. After the war, because Woodrow Wilson was willing to give his British and French allies anything for his failed League of Nations scheme, he not only let them tromp all over Germany by inflicting war guilt and reparations but let them steal overseas colonies from Germany and its ally, the defunct Ottoman Empire. The British and French both wanted Middle Eastern oil, so they drew artificial boundaries in Iraq, Syria, Lebanon, and elsewhere that didn’t correspond to the lines of their ethno-sectarian inhabitants. The conflict in all these places today is a result of World War I and its aftermath.

However, unfortunately most Americans view an interest in history as quaint or nerdy. Thus, their ill-informed nature allows politicians like Hillary Clinton, John McCain, and Dick Cheney to selectively mine history for lessons that will justify their often aggressive and ill-advised preferences for today’s U.S. overseas meddling. That is why remembering back far enough is really important.