There’s a lot of ambiguity in the word “intervention,” with interpretations ranging from a single bombing raid to fully going to war. What do you think is the right course?

The short answer is I don’t know. There’s a tremendous amount of intelligence one would want to look at to answer this question. It’s always true, but in this case it’s particularly true, that the best you are going to do is probabilities. Most advocates only look at the probabilities on one side. Those who don’t want to intervene talk about the probability of things going wrong, which absolutely exists; there’s no way to get rid of it. Those who want to intervene focus on the probability of damage if we don’t intervene, and there we have a higher degree of certainty, because we’ve already seen 125,000 killed.

Within that context, you have to look at a set of tactics. A lot of people seem to be dismissing the idea that there’s any role for a surgical, strategic strike short of regime change. While I have advocated for a more aggressive posture that would potentially include regime transition, there is absolutely an argument for inflicting some cost to the regime for the use of chemical weapons against the civilian population.

What is that? I would say there’s some value to crippling some part of the military infrastructure, which would relate directly to the capacity for using chemical or biological weapons, or other infrastructure. And that I think you can do largely from the air without a lot of involvement on the ground. Simultaneously, there has to be a continuation of the diplomatic engagement we’ve been doing.

But if the objective isn’t regime change, what is the objective? Aren’t you weakening the regime and allowing the rebels to gain an upper hand in the civil war? Is the point really just to make a statement in the hope other irrational dictators would be deterred by it in the future?

There is an interest, not just by us but by the community of nations, in creating a significant disincentive to the use of chemical and biological weapons, which even repressive regimes, on the whole, have treated as off-limits. This is a technology that allows regimes who do not want to bomb their own civilian infrastructure to kill and do damage to a great number of civilians. [Syrian President Bashar al-]Assad clearly has been escalating and will consider doing it again. When he does, he is going to make some assessments about whether the benefit he gets domestically from using those weapons is larger or smaller than the cost he has to pay for using those weapons. Even if in some ways he is well beyond all rationality, he is going to make that calculation.

You think an irrational dictator whose objectives are focused on defeating internal opposition is going to respond to incentives?

It’s part of his calculation. He knows if we intervene, his days are over, so part of what he’s doing, like a petulant child, is seeing how far he can push before we come in. Traditionally, the use of chemical and biological weapons, with very few exceptions, has been something you cannot do without invoking dramatic action.