This being the 100th anniversary of the outbreak of World War I, I have plunged into several books on the subject, most of them relating to what started it, and I have come up with the following conclusion: mustaches. Most of Europe’s leaders had either a mustache or a beard — the German kaiser, the jejune Wilhelm II, had the most resplendent mustache of them all, “fixed into place every morning by his personal barber,” Margaret McMillan tells us in her new history of the road to war. This confirms what I always thought: The Germans started the war.

I am being a bit of a smarty-pants here, although my mustache theory is as good as anyone’s. The war killed at least 16 million people and changed history on a dime, creating the modern Middle East, for instance, and setting the stage for World War II, and yet it is still unclear what caused this epic conflict. Was it alliances? Was it nationalism? Was it the arms race or a variation on that theme, capitalism with all its alleged evils?

I am severely underqualified to provide an answer. But the sheer irrationality of the war does offer a lesson: Expect the unexpected. Leave room for irrationality. Respect the role of emotion and remember that most men fight for the man next to them, not for their country or some great cause. In the end, though, that sucker trait is used by countries and great causes. It doesn’t really matter why you fight, just as long as you fight.

I exhume World War I not just to mark its centennial but also for a purpose. The war ended after the United States got into the fray. America then reverted to its traditional isolationism and we got, partially as a result, World War II. Now we are reverting once again to a form of isolationism — not as extreme as the first, but the emotion is there, this time even more so on the left than on the right. On the left, anyone who suggested that the U.S. intervene early in Syria, when the Assad regime might have been toppled without resorting to putting boots on the ground, was denounced as a war-monger. I am tempted to say that the United States did nothing. Actually, it was worse than nothing.

Those who believe World War I was caused by a crazy-quilt of alliances among the European powers may shudder at the ones America has now. We are obligated to defend Japan, and we are obligated to defend South Korea. Both countries have issues with one another and, more important, with China. Japan and China contest a group of islands, and China and South Korea contest a different area of the East China Sea. None of this is worth the life of a single person.

But in the Far East, what concerns South Korean, Japanese and other policymakers is not just the potential instability of the region but also the Obama administration’s erratic Syrian policy. A “red line” was pronounced, then ignored. Force was threatened by the president, and then the decision was lateraled to Congress where, to further the metaphor, the ball was downed and, just for good measure, deflated. None of this comforted the nations that see China as a looming menace and rely on the United States for backup. “[T]he administration’s prevarications over Syria continue to linger for the elites who drive national strategy in these countries,” wrote Michael J. Green , senior director for Asian affairs at the National Security Council under President George W. Bush.

The Syria debacle, coupled with the consensus that the United States is turning inward, is bound to produce instability. The South Koreans, in particular, have to worry if the Dear Leader in the North considers President Obama to be a paper tiger. The Japanese have to worry whether the Chinese have reached the same conclusion. The United States’ European allies worry that the United States has pivoted to Asia. In Asia, the worry is that the proclaimed pivot is just a rhetorical device.

In 1996, Madeleine Albright popularized a phrase used by President Clinton. She repeatedly called the United States the “indispensable nation.” The phrase lends itself to mockery, but it is dead-on. Nowhere is the United States more indispensable than in the Far East, where a rising China, acting like pre-World War I Germany, is demanding respect and flexing its muscles. It’s all too familiar: rising nationalism, excessive pride, irrationality ready in the wings and America going into its habitual hibernation. Only the mustaches are gone.

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