This is the first part of a three-episode series examining the post-9/11 world for the 20th anniversary of the al-Qaeda terrorist attacks.

In 1915 one of the most popular songs in America was a somber lament. "I Didn't Raise My Boy To Be a Soldier" inspired a peace movement of socialists, radicals, and civil libertarians in a nation whose people were deeply skeptical of military interventionism. It is hard to imagine such a song climbing to the top of the charts today.

The modern notion that America is obligated to dispatch thousands of troops across the oceans, to paraphrase Woodrow Wilson, to make the world safe for democracy, did not drive foreign policy then. Historian Michael Kazin discusses the absence of any major peace movement in the U.S. today compared to the influential antiwar activism of the past century. Unlike the 1960s, when the nation was roiled by massive demonstrations against the Vietnam War, antiwar activism in 21st century America is quiescent, despite the fact the U.S. has been in a state of constant war in multiple countries since the 9/11 terrorist attacks.