Secretary of State Kerry had a very interesting conversation with +Nicholas Kristof
and Lara Setrakian today. While a lot of it was the usual nonsense, I think that one useful piece of information did come out about the reasons and objectives for US involvement. While chemical weapons are the casus belli,
the argument for their being actually relevant to our decision is tenuous at best. The real calculation is this: at the end of the war, there are three realistic options.
(1) Bashar al-Assad maintains power.
(2) Some other powerful figure manages to establish control over a united Syria -- essentially, an alternative dictatorship.
(3) Syria collapses and breaks up, forming a failed state in the style of Afghanistan or Somalia.
Option 3 is very bad for all concerned, because such a failed state would become an operational base for every major terrorist group on the planet -- not just big ones like Hezbollah and al-Qaeda, but also the local ones like al-Nusra who (as Secretary Kerry pointed out) make al-Qaeda seem warm and friendly by comparison. (The Middle East really does specialize in "you thought those
guys were bastards?")
Reaching option 1 or 2 requires that an actual peace negotiation ultimately happen between people who can credibly represent their sides. Option 1 is considered bad by the US because our relationship with al-Assad is so bad, because his support for and involvement with terror organizations is so deep, and because he has indicated so much willingness to cause trouble. But so long as al-Assad feels that he is winning, he isn't going to come to the negotiating table, and option 2 is effectively ruled out.
So the real objective is to weaken al-Assad's forces enough to make a Geneva II conference a palatable alternative to him, presumably including him surviving and being exiled (together with a lot of money) to Russia.
All told, I don't find this entirely unreasonable -- he also mentioned, although obliquely, a significant increase in support to the "moderate opposition," including particularly General Idris, whom he referred to as "a very forceful individual." (This being diplomat-speak for "he would be an effective dictator, and will be, if we have anything to say about it") Given the set of options in play, this may be the least bad one.
The downsides, however, are many. In an option 2 world, we still have a dictator who is likely to have to be quite bloody-minded in order to maintain power. (Just like the al-Assads were) It's by no means unlikely that said dictator will have to make alliances with several of these terror groups, letting them effectively operate freely in certain areas so long as they support his rule. (cf the relationship of the Saudi government with various rather alarming Wahhabi organizations, or the "tribal areas" in northwest Pakistan which are only nominally ruled by the government) And genocide of some sort is quite likely, especially against minority groups which are associated with al-Assad: both is own group (the Alawites) and the groups which allied with the government in power in order to survive. (e.g., the Druze and the Copts)
This is one of those moments when politics is all about choosing the least terrible of quite a few terrible options. I'm still not convinced that heavy bombing is the best idea, but if it's intelligently targeted towards weakening both al-Assad and his less savory allies (e.g. Hezbollah) then it could be quite productive. Weakening Hezbollah would, in fact, be a great way to reduce the chances of many other wars in the area over the next few years, as well as weakening Iran's government in a plausibly deniable fashion.
But this will all boil down to details -- exactly what, where, when, and why.
(NB: There's also talk about a proposed deal for Syria to give up their chemical weapons to Russia. This is just negotiating tactics, as far as I can tell; there is nothing about this deal which is even remotely plausible. Even if everyone agreed to it tomorrow, the logistics aren't merely prohibitive, they're ludicrous)