Disbanding the army may have been an error
Who knows? We have certainly made mistakes.
It would not seems to be that difficult to reconstitute the army under officers not loyal to Saddam. Assuming it consisted of a willing fighting force.
If they had left the army in place I suspect there would have been accusations of establishing a military dictatorship by way of Saddam's commanders.
Overall it seems to be a minor point but valid enough to trot out another Bush detractor.