.As Mr. Assad’s military arsenal has dwindled, he has turned to indiscriminate aerial warfare. In May, his air forces accounted for more than 65 percent of all civilian casualties in Syria. In May 2014, that number stood at just 35 percent.

The leading killer in Syria today is not ISIS or Al Qaeda; it is Mr. Assad. According to the Syrian Network for Human Rights, in 2015, his forces have killed seven times the number of people that ISIS has and were responsible for 75 percent of all civilian deaths.