The wars the U.S. government has fought since the attacks of Sept. 11, 2001, have forced 37 million people—and perhaps as many as 59 million—from their homes, according to a newly released report from American University and Brown University’s Costs of War Project. Until now, no one has known how many people the wars have displaced. Indeed, most Americans are likely unaware that U.S. combat operations have taken place not only in Afghanistan, Iraq and Syria, but also in 21 other nations since President George W. Bush announced a global war on terror. Neither the Pentagon, the State...