"If you don't know, don't do."

I don't think you can ever know. That's the nature of war.
The Gulf I war simply couldn't have worked as planned- how could you expect that Saddam would have signed a cease fire agreement within 100 hours of ground campaign? If That was the "plan" then the planner would be been fired for incompetence.
In Gulf II I don't think we really expected to actually get to Baghdag within 3 weeks. Saddam's "plan" obviously didn't work, and the terrorist's "plan" obviously didn't work, in fact the terrorist "plan" is almost as though they were "on our side" it is working so poorly; they managed to turn the majority of population of the entire region completely against them.

Wars aren't predictable. If wars were predictable Saddam would be holding Kuwait. Even bombing a target and declaring victory isn't predictable. Wars are never predictable.