The diplomatic situation had been looking bright for President Bashar al-Assad of Syria. With the help of Russia, he had consolidated his power, the rebels were on their heels and the United States had just declared that ousting him was not a priority.
So why would Mr. Assad risk it all, outraging the world by attacking civilians with what Turkey now says was the nerve agent sarin, killing scores of people, many of them children? Why would he inflict the deadliest chemical strike since the 2013 attacks outside Damascus? Those attacks came close to bringing American military retaliation then. And in
