You've got money. But what do you want to buy?
Victor Davis Hanson's comments at Pajamas Media on the utility of sending additional forces to Iraq contain two items whose importance can probably not be overemphasized.
Enlarge the planned Iraqi security forces to near 400,000, and embed far more Americans in those units.
Recalibrate the ratio of support to combat troops, so that we don’t simply create bigger compounds to facilitate larger troop levels to end up with more stationary and more numerous targets—and ever more enclaves of Americans behind thousands of acres of bermed reserves.
So spell out the mission, the new rules of engagement, and then, and only then, surge—if need be— more troops.
By far the single most critical item of the two is to "spell out the mission". US policy, up until now has been to establish a fairly democratic and preferably unitary successor state to Saddam as a follow-on to deposing the dictator. While Saddam has unquestionably been deposed, the possibility of a democratic successor state is fundamentally one that Iraqis must settle.
For as long a democratic Iraq remains an American goal the suggestion, "to embed far more Americans in those units" becomes important because it helps prevent, or at least moderates, attempts by Iran and Shi'ite elements to turn Iraqi state organs into sectarian institutions. With Iraq already a formally independent country it is vital that America retain some direct leverage over local military institutions while the democratic character of the successor government remains a US goal. Ironically, a praetorian veto over sectarian politics is compelled for as long as Iraqi democracy remains an American goal if only to prevent the institutions it has established at great cost from being turned into vehicles of partisan warfare. While it may be true that consensusal democracy can't be established at the point of a gun, it is undeniable that nothing prevents the tyranny of guns so much as another gun -- in this case in American hands.
But if the US disavows any compelling interest in the democratic character of Iraq, the necessity to retain a direct influence over the Iraqi armed forces largely vanishes. Iraqi becomes simply another foreign country in the Middle East, whose internal politics is irrelevant, to be wooed or compelled by instruments of US power according to American geopolitical interest. In that case, it becomes conceivable, though inconceivably gruesome, to throw a net of military safety around the Kurds, let the Shi'ites and Sunnis settle accounts with arms folded, and then deal with the last group standing until it is amenable to American will, and conveniently settling the hash of the Sunni insurgency and checkmating Iranian ambitions at a stroke. This mentioned simply by way of illustration, not advocacy, to highlight how the utility of any proposed reinforcement varies with the mission. It is the mission that provides the standard for success and the guide for what the force should do.
The attempt to establish a democratic Iraq, however disappointing the experience has been so far, is unlikely to be abandoned very easily in the near future -- and perhaps not for as long as a the ghost of a shadow of a chance remains that it may be attained -- not only because the current administration is so invested in it, but because the alternatives of divide and rule and naked power politics, which would have been adopted without a second thought by Empires in the early 20th century, are too cold-blooded and heartless to be easily embraced by an American public which genuinely wishes the Iraqi people well.