All the carping over Rumsfeld came from the left. Rumsfeld may have been "in over his head", but that's not to say he had commanders in the field of battle reporting back to him. They're the ones who decide if we need more or less troops.
It didn’t all come from the left. Remember that they ran editorials in the Army Times, Navy Times, and Air Force Times calling for his resignation.
That’s not exactly a vote of confidence...