In the engimatic words of Donald Rumsfeld, "Stuff happens." In war there are simply too many variables to reasonable predict any and every consequence. And when your first priority is to protect the lives of your soldiers, other objectives may falter.

I think its too early to judge the success of regime change in Iraq. Its still entirely possible that the country could devolve into futile funk with various faction fighting each other with U.S. forces caught in the middle. Its also entirely possible that the country will quickly stabilize. We could plan for any and all contigencies and still find ourselves surprised. There are no guarantees.