The marginal product of war

Tyler Cowen writes,

The correct marginal question...compares the current badness to the badness which would have resulted after the reign of Saddam (or his sons? grandsons?) ended, however that might have happened. Today we see many signals that things are going badly. But most of those signals also imply that things would have gone very badly under the alternative scenario for Saddam's fall. A civil war, for instance, may well have happened anyway, albeit later.

(emphasis his)