One hundred years ago today, the United States declared war on Germany and entered World War I after the advent of unrestricted submarine warfare and the disclosure of the Zimmermann Telegram, in which the Germans sought Mexico as an ally. It was an industrial war of attrition, with the carnage born of machine guns, warplanes, tanks and the first use of chemical weapons, and millions already had died in the trenches. A naive America, which didn't know its own strength but already was the world's dominant economy, entered the war idealistically.
America's might helped push the Germans to defeat in November 1918, but not before more than 53,000 Americans died in combat. No longer innocent, the United States took the exact wrong lesson from the war and became isolationist in outlook until the attack on Pearl Harbor a generation later shook the nation from its torpor and made it the world leader it remains today. A great nation cannot stand apart from world affairs. In fact, inaction is itself a choice — and usually a bad one.
Now, as the world reels from the ghastly images of a chemical attack that killed scores of innocents in Syria and a rogue leader lobs midrange missiles provocatively from North Korea, the United States is being tested again. President Donald Trump will host Chinese President Xi Jinping in Florida today. As the leaders of the world's two largest economies meet, Trump will have a chance to assert U.S. leadership, to declare what it stands for in the world. And perhaps more important, what it won't stand for under any circumstances.