In the gruesome, bloodstained years after 9/11, it seemed like the United States learned a painful lesson: There are limits to American military power. Bush-era disasters in Afghanistan and Iraq seemed to prove to much of the country that constant and aggressive use of U.S. military force abroad only reinforces the regional chaos that is the ultimate source of strength for extremist groups like al Qaeda and ISIS. For awhile there, even neoconservatives were shamed by the rivers of blood unleashed by their wars of aggression.