Any situation short of the Islamic State obtaining nuclear weapons, and the United States knowing about that, appears to mean that President Obama will not order American ground troops into battle to destroy the terrorist group. Over the weekend, ISIS beheaded a third American, former Army Ranger turned aid worker Peter Kassig. But a day before that news broke, President Obama outlined an extreme scenario under which he would order troops to fight ISIS on the ground in Iraq and Syria. The president made his remarks at the G20 Summit in Australia Saturday. Obama says that he would send ground...