Rumsfeld thought that the grateful Iraqis would come together, create a new government and be our faithful allies for ever more. Had he believed we would be in for several more years of combat we probably would not have been so eager to start that fight. As I recall, he had a lot company sharing those opinions including a sizeable number of Freepers.
Watch this five part series with four star General Jack Keane. It isn’t pretty. It describes how basically Petraeus, him and a handful had to find Vietnam era operations manuals and near literally blow the dust off them. That was the state of Army thinking at the time, which basically was zero.
Rumsfeld wasn’t responsible for that.
Keane basically gives the impression that each kept to his own knitting and no one integrated or had a coherent idea, or ideas as how to proceed.
Keane is the first person I’ve seen give his view, publicly. Gut wise he’s pretty believable. Not a perfumed, managerial type General at all. He seems very down the middle of the road type.