Assad had promised to turn over all his chemical weapons back in 2013, and Russia promised to monitor that Assad had actually done so. Clearly Assad had not done so.
That said, this has all the hallmarks of a Mattis operation. It is limited to a strike at a military target. The target was coordinated with the Russians to make sure none of their assets were under the missiles. It is proportionate to the offense involved — the violation of an agreement to destroy chemical weapons. It has the possibility for a diplomatic aftermath where the US doubles down on demanding the destruction of chemical weapons, assuming that the State Department has anybody left who speaks Arabic and understands diplomacy. It is not, in other words, a full-scale declaration of war. It is not the 3ID and 4ID wading ashore at Tripoli to take a little jaunt down the highway to Damascus while the 101st Airborne roars in on choppers.
Whether the Trump Administration handles the diplomatic aftermath such that we don’t end up at war with Russia… we’ll find out, I guess.
– Badtux the News Penguin