My friend Jeff has a post up about the death toll in Syria. It includes some comparative observations, this among them:
[I]t might be worth adding one more comparative reflection. Since the political upheavals of the so-called "Arab Spring" began a few years ago, some people who think that the 2003 Iraq war was a terrible mistake and an unmitigated disaster (a position for which there are certainly good arguments, given what happened to Iraq and the Iraqis after 2003) have wondered whether these developments provide additional evidence that the overthrow of Saddam Hussein and his regime by external force was simply unnecessary. If Saddam Hussein had just been left alone, and his regime had survived into the present decade, wouldn't some Iraqi version of the Arab Spring have led to his overthrow in a way that was less painful and costly to Iraqis, to Americans, and to everyone else?
It's hard to answer that question for certain, of course. But based on the historical record, including the bloodbath with which Saddam Hussein crushed the national revolt against his rule after the 1991 Gulf War, I think it's possible to offer some plausible predictions. If the Ba'ath regime headed by Saddam (or one of his psychopathic sons) had still been in control of Iraq during the past few years, and had been faced with a serious challenge to its grip on power, it's probably safe to expect that the response would have made what's happening in Syria now pale by comparison.
Would the results have been even worse than what happened in post-Saddam Iraq during the past decade? Again, one can't say for sure, and no one should pretend otherwise, but that possibility certainly shouldn't be dismissed. Let's even be extra-optimistic and assume that a hypothetical Iraqi Spring would have overthrown the regime. In the very best of circumstances, the death throes of the Iraqi Ba'ath regime, along with the aftermath, would almost certainly have been extremely gruesome.
At the time the arguments over Iraq were most intense, opponents of the war tended to glide across, or entirely ignore, the counterfactual costs - those of leaving Saddam in power. What Jeff says here is pertinent. His post is worth reading in full.