In 2008, then-Sen. Barack Obama campaigned for president promising to extricate the United States from its grinding wars in Afghanistan and Iraq. His administration, Obama hoped, would be known for domestic programs rather than war-fighting. Unfortunately America’s adversaries had different intentions. Obama has now been at war longer than any other U.S. president.

A case can be made that America’s ongoing military involvement in Iraq, Afghanistan, Libya, Yemen, Syria and elsewhere does not constitute “war” in the constitutional and strategic senses of the word. But it is clear that armed strife is the new normal, not an episodic aberration as it was for most of U.S. history. Even so, Americans have not yet fully come to grips with the idea of persistent conflict, instead clinging to the hope that once al-Qaida and the self-styled Islamic State are defeated, peace will return. This will not happen. ...