If I understand correctly, the “realist” view of foreign affairs is that states act entirely on the basis of objective national interests (as best they understand it). Ideology or sentiment may be deployed to rationalize policy, and thereby justify its costs to the citizenry, but it isn’t the driver of policy. Therefore, changes in regime – even radical changes in a regime’s character – don’t generally change foreign policy, because they don’t change that configuration of interests.

There’s obviously some truth to this, but there are also obviously limitations to any such completely reductionist theory. Of course, you can complicate the model by distinguishing “regime” interests from “national” interests, or by deploying an interest-group model of internal regime politics, and then seeing how interest-group interests might deform foreign policy away from the national interest, without positing the existence of forces other than interests that drive policy. But make the model sufficiently complicated and it ceases to be predictive.

But what possible interest-based model of foreign policy explains the Obama Administration’s recent decision to intervene, even modestly, in Syria?

The Assad regime is exceedingly nasty and not particularly friendly to America – but neither is it an important antagonist, and Syria has proved willing to deal with America in those rare instances when our interests have converged. The collapse of Syria into chaos potentially creates serious problems for American allies like Turkey and Israel, but this is an argument for either mediating an end to the civil war or tacitly accepting an Assad regime victory, not for intervening on the side of a fractured and highly questionable opposition.

Dan Drezner makes the argument that, in fact, American interests are served by prolonging the Syrian civil war, because this drains resources away from Iran and Hezbollah. This sounds like a version of the old “flypaper” justification for the occupation of Iraq – better Iran and Hezbollah should be fighting in Syria than . . . here? As with Iraq, the justification evaporates upon examination. Longstanding conflicts don’t weaken extremist groups, they add to their resources – even as they drain the overall resources of the society. A prolonged civil war will certainly weaken Syria, but I don’t see how it will materially weaken Hezbollah in Lebanon. And I’d be curious to see numbers on just how much of a drain the Syrian conflict is on Iran, even in monetary terms. Most importantly, what about the radicalizing effect of a prolonged civil war on Sunnis in Iraq, Saudi Arabia, Yemen, Egypt, etc? I was under the impression that preventing that radicalization was a really big foreign policy objective. And last, there’s Daniel Larison’s point that if the goal is to prolong the civil war, it’s counter-productive to put American credibility on the line by publicly choosing sides. It would be far more sensible for us to covertly support the rebels while publicly advocating a peaceful resolution of the conflict. Drezner’s argument feels like an attempt to impose coherence on a policy that is driven by other factors.

Is there an interest-group explanation for American policy? Israel has no love for Assad, but the Israelis are more concerned about the possibility of chaos on their northern border than anything else, and are far from sanguine that a successor regime would be any more friendly than Assad’s has been. The American oil industry has no reason to favor instability in the region, and has no particular interests in Syria. The “military-industrial complex” gains little from our involvement in these kinds of bloody messes on the ground, and it’s a stretch to see how involvement in Syria is going to help sell more drones or bombers, except as an instance of the general rule, “more war is good.” Unless you believe there are literally no tradeoffs, Syria seems like a bad square on which to place the kind of bet that could pay off with large contracts.

What does that leave? Three possibilities come to my mind.

First possibility: we’re doing it for our Arab allies. America’s Sunni allies – Saudi Arabia, Egypt, etc. – clearly favor a rebel victory. Arguably, we are doing them a favor. At the time of the Libyan adventure, I understood American policy as basically being driven by a desire to “help” France (and, to a lesser extent, to UK), which strongly favored intervention. And France wanted to oust Qaddafi because their client had just been driven from Tunisia without Paris lifting a finger to support him; it would just look bad if “people power” could topple a French-backed dictator but not a dictator who had worse relations with the West (or, worse, was backed by Italy). Our policy also appeared to be driven by a desire among the Gulf states to get rid of a guy who had been a persistent annoyance in the Arab League. But actually committing to a rebel victory in Syria is a much bigger favor. And it’s really unclear what we are getting in exchange. I’d like to see a realist actually do the “pro-” and “con-” analysis on this one before I’d accept that we’re publicly arming the Syrian rebels because we “need” to satisfy our Sunni Arab allies.

Second possibility: we’re doing it to influence the rebels. It’s possible that we see a rebel victory as a realistic prospect, and want to make sure that we have “friends” among the victors. In particular, we want to make sure that anti-American terrorist groups don’t wind up dominating a post-Assad Syria. The problem with this idea is twofold. First, it’s not clear that this sort of strategy works – it’s not clear that these kinds of friends stay bought once the smoke clears, nor that we don’t wind up merely pushing rival factions into more open opposition to America. But that’s a lesson we never seem to learn, so put it aside. More importantly, the timing doesn’t work. America is stepping up its support for the rebels at the very moment that it’s widely reported that the Assad regime is winning. If we were trying to curry favor with rebel factions, we’d have gotten involved much earlier.

The third possibility: that the American government sees itself as necessarily implicated in the Syrian conflict simply by virtue of our deep involvement across the region, and so cannot plausibly avoid being blamed for whatever outcome transpires. We cannot, in other words, have a hands-off policy – the only question is what our hands will be seen doing. And they need to be seen as doing something that has a positive propaganda value internationally. This is, roughly, the justification that was offered for intervention in Bosnia-Herzegovina and later in Kosovo: that it would be “unacceptable” for the Serbs to get away with massacres and ethnic cleansing in the “heart of Europe” and therefore America needed to engineer, by some combination of diplomacy, military aid, and outright military intervention, a resolution reasonably favorable to the non-Serb side in the former Yugoslavia.

I see two problems with this analysis from a realist perspective. First of all, it seems clear that the advocates of intervention are creating the situation that they ostensibly are concerned about: the implication of American credibility in conflicts far from any direct American interest. From a realist perspective, why would a regime continually extend its credibility further in order to preserve it from challenge? Isn’t it obvious that this describes a kind of foreign policy equivalent of a Ponzi scheme?

But the bigger problem from a theoretical perspective is that this stretches the definition of “realism” to the breaking point. If a “realist” explanation of America’s Syria policy is that the American regime sees its interests as served by promoting the notion that America is the global hegemon responsible for problems that it did not clearly cause, cannot clearly solve, and that do not directly implicate its interests, then that’s as much as to say that “realism” is not a realistic policy for America. At which point, what’s left of realism as a theory?

Hence my original question. Is there a convincing realist explanation for America’s Syria policy? And if not – if American policy is being driven by forces divorced not only from the national interest but from a clearly-discernable parochial interest of the regime or powerful interest groups – then what are the implications for realism as a descriptive theory of foreign affairs?