Defense Secretary James Mattis said on Friday that he believed the leader of ISIS, Abu Bakr al-Baghdadi, was still alive. “I’ll believe otherwise when we know we have killed him. We are going after him," he told reporters at the Pentagon. The Russian military said last month that it had struck a meeting of ISIS leaders in May and possibly killed Baghdadi. The British-based monitoring organization, the Syrian Observatory for Human Rights, then said it had obtained information from senior ISIS commanders confirming Baghdadi's death.