"...my gut instinct would be to have our unbridled forces move against Sadr and see by commitment which side the new Iraqi government takes. Their deeds, not words will identify them as friend or foe."
most recently the prime minister sided against us by forcing us to take down checkpoints as i understand it around Sadr city in looking for one of our troops, i.e. he was not strong enough or if playing a double game did not want to move that strongly against Sadr. from an Iraqi standpoint, they have to be worried about America's commitment (especially during our election season) while we are asking them to put the lives of their families on the line.
the jihadiis think in terms of generations, not a few years. unless the PM thinks we will be committed to see this thing through to success, he cannot gain the support he needs from his own internal allies to make the ultimate sacrifice. so a short term "test" absent this longer and larger commitment of each to the other imho will not tell us if it is win-able. If we get the PM's commitment and we in turn give ours and then together move against Sadr, that would be something else again in what we might learn. If we then found the PM was misleading us, our commitment would no longer be binding.
I'm assuming the PM has felt the current level of America troops was not going to be enough given the size of the challenge in moving against his radical wing, and he has shown ambivalence as a result. A seize and hold force on our part and a full commitment to move against their radical wing on their part hopefully can put this over the top. But it has to start with the PM's commitment in word and deed based upon in turn our commitment to his commitment which then allows him to make the full commitment which he would be powerless to do otherwise (my speculation).