Putin doesn’t care one way or the other about chemical weapons. Nor about dead Syrian children. Nor about international norms, parchment treaties and the other niceties of the liberal imagination.
He cares about power and he cares about keeping Bashar al-Assad in power. Assad is the key link in the anti-Western Shiite crescent stretching from Tehran through Damascus and Beirut to the Mediterranean — on which sits Tartus, Russia’s only military base outside the former Soviet Union. This axis frontally challenges the pro-American Sunni Arab Middle East (Jordan, Yemen, the Gulf Arabs, even the North African states), already terrified at the imminent emergence of a nuclear Iran.
At which point the Iran axis and its Russian patron would achieve dominance over the moderate Arab states, allowing Russia to supplant America as regional hegemon for the first time since Egypt switched to our side in the Cold War in 1972.
The Administration either doesn't understand the stakes, or doesn't care about the stakes, or has no clue how to achieve them. Or all three. Or pick two. It's impossible to tell, based on conflicting statements and multiple threats to take immediate inaction.