I'm not so sure this is true. There have been plenty of "top military brass" that have suggested alternatives from before this war even started (more troops initially, not dissolving the Iraqi Army, etc). The problem is that the administration keeps removing people that present ideas they don't like. The net effect is that it always LOOKS like the military wants more troops and escalation.

Just as the administration leaked/planted stories in the press (NY Times specifically) about WMD and then used those stories as "evidence" that WMD's existed, they are doing the same thing with military planning. They put someone in that will say what they want to hear and then use that statement as rational for action... completely circular arguments.