So why did Bashar al-Assad launch a chemical weapon attack in the first place? It's a bit of mystery. McClatchy rounds up the evidence, including a new report from Der Spiegel about a phone call intercepted by German intelligence:
According to Der Spiegel, one of the parties in the intercepted phone call was a “high-ranking member of Hezbollah,” the militant Lebanese movement that’s sent fighters to support the Assad government. That Hezbollah member told the Iranian that “Assad had lost his temper and committed a huge mistake by giving the order for the poison gas use," according to the magazine’s account.
The U.S. intelligence assessment reached a similar conclusion, finding that the alleged use of chemical weapons may have been in part because of “the regime’s frustration with its inability to secure large portions of Damascus.”
....The German account goes further than others that have been released recently in providing details of Assad’s state of mind that might have played a role in the motivation for launching a chemical attack, noting that Assad sees himself embroiled “in a crucial battle for Damascus.”
It also said Assad’s forces had used a highly diluted chemical agent in previous attacks on rebels and that the high death count Aug. 21 might have been the result of “errors made in the mixing of the gas” that made it “much more potent than anticipated.” That would be consistent with a suggestion from an Israeli official, cited by The New York Times, that the attack was “an operational mistake.”
So it was all one big FUBAR, launched by a sociopath who lost control of himself and then bungled by a military unit that was incompetent. And now we're deciding what we ought to do about it.