Planning for the War and later

I know nothing of war and plans and strategies etc. Without "everyone" including military people thinking that the aftermath of the war in Iraq was a surprise, I would have assumed that it all went basically as planned. Perhaps the plan B, but still, as planned.

Neo-Neocon has a long 2 part piece concerning this that I found interesting.
Part one.
"One of the most common arguments against the administration's planning and conduct of the war is that it underestimated the resistance that would be put up, saying that it would be a "cakewalk," and that later events proved them utterly wrong. Is this true? Who made the "cakewalk" prediction? And to what aspect of the war was he actually referring? And why was that resistance or insurgency (or whatever name we give the terrorism and sabotage that has gone on in the aftermath of the war) seemingly worse than anticipated?"

Part two. (besides pointing out that no one in the administration said it would be a "cakewalk")
"Did the President and key members of his Administration foresee how exceedingly difficult it would actually be to accomplish this? I don't think so. Should they have? Perhaps.

But what really matters now is: do they have the patience, intelligence, will, and determination to get it right? My answer: they do--if we do."