Given that the Syrian government's use of chemical weapons—or perhaps its latest use of chemical weapons—has been the particular atrocity that is likely going to lead the United States to war, the logic behind this rationale is worth exploring. My friend and colleague John Judis, in a piece titled "Obama's Biggest Gamble," explains the risks of President Barack Obama's decision to seek congressional authorization. He concludes by writing:

So who is to act if not the United States? Who will enforce the "red line" on chemical weapons? One can dream about the revival of the United Nations or about a new international organization to displace it, but that prospect is decades away. If the United States cannot act—or if it can't mount a credible threat in lieu of acting—then the world as it now exists is unlikely to coalesce into a new international order. More likely it will descend into a Hobbesian chaos.

Meanwhile, in The New Yorker, Steve Coll lays out the reluctant case for action, which he also bases on the use of chemical weapons by Syrian forces. This is Coll's historical analysis:

Saddam saw great value in chemical arms during the nineteen-eighties, and his twisted logic bears examination in the light of Syria’s deteriorating conflict. Saddam first used gas bombs to thwart Iran’s zealous swarms of "human wave" infantry. Chemical terror broke the will of young Iranian volunteers, a lesson that informed [the] subsequent Kurdish campaign. The Reagan Administration’s decision to tolerate Saddam’s depravities proved to be a colossal moral failure and strategic mistake; it encouraged Saddam’s aggression and internal repression, and it allowed Iraq to demonstrate to future dictators the tactical value of chemical warfare. The consequences of similar passivity in Syria now are unknowable.

If I am reading Coll correctly, his argument is as follows: twenty-five years ago, Saddam used chemical weapons against both Iran and his own people. In the first case, the world did nothing (while America actually aided him), and in the second case America and the international community decided against retaliatory action. Then, for the quarter-century before Assad's crimes, there were no major uses of chemical weapons.

I suppose one could argue that Assad would not have used chemical weapons if the United States had acted against Saddam in 1988, but the general lack of chemical weapons use over the past 25 years is a sign that the taboo against their deployment is rather robust, even absent military intervention by the United States.

To argue that we should act in Syria because of the use of chemical weapons is to assume that other cornered dictators—the worst of the worst—will not use them in the future because the United States entered into conflict with Syria. Even if one assumes that brutal strongmen faced with extinction can be dissuaded from using these horrible weapons, is anyone going to take the lesson from a (limited) American campaign, with weak international support, that chemical weapons can never be used? I doubt it.