Jackson Diehl starts his latest column on a promising note: "For five years Washington-based officials and pundits have repeatedly made the mistake of predicting that the next six or 12 months in Iraq would be decisive." He then, however, just goes on to engage in the same fallacy: "Yet, for once, saying that the next six to 12 months will win or lose the war just might be right." And it becomes even less promising from there:

The number of American soldiers in Iraq started coming down last month. By July it will have dropped from the peak of 180,000 it reached briefly in November to 130,000, or 15 brigades, the force level before the surge. The Pentagon has until March to judge how Iraqis react to the initial withdrawals -- whether violence in volatile places such as Anbar province remains low or escalates again as U.S. troops depart. Then another decision will be made, on whether to reduce the force by five more brigades, to a total of about 100,000 troops, by the end of 2008.

This decision ought to be based entirely on whether Iraq's progress can continue with an American force 40 percent smaller than it was at the surge's peak. But external politics is already intruding: Gen. George Casey, the architect of the failed U.S. military strategy in Iraq pre-Petraeus, is already pushing for the full reduction, on the grounds that the Army needs to reduce its exposure in Iraq. Defense Secretary Robert Gates, whose strategic preoccupation has been arriving at a force level in Iraq that could win bipartisan acceptance in Washington, has said publicly that he'd like to hit the 100,000 target.

The idea that America's policy toward Iraq "ought to be based entirely" on conditions in Iraq, and that anything else constitutes the intrusion of "external politics" is really foolish. When considering US policy toward Iraq -- or toward Mexico or Afghanistan or Kenya or Pakistan or Russia or wherever else -- we have to try to do the right thing all things considered. To observe that were we willing to commit an unlimited quantity of resources to the country for an unlimited period of time we might be able to improve conditions in Iraq is silly. Suppose we dedicated infinite resources to security and economic development in nearby Haiti? Or Jamaica -- slightly further away, but conveniently inhabited by English-speakers? Our willingness to spend hundreds of billions of dollars in Jamaica forever and ever ought to be based entirely on the crime and unemployment rate of Kingston, but unfortunately external politics is already starting to intrude.

But, of course, nobody would write something like that. But if General Casey thinks we need to expeditiously reduce our force levels in Iraq to 100,000 in order to rescue the Army from dangerous "overexposure" to Iraq, isn't that worth taking seriously on the merits? Diehl doesn't seem to want to grapple with it, but Casey and the joint chiefs seem to me to believe that because it's true. Now Diehl also says that if we reduce to that level, the security gains of the "surge" are likely to go away. I tend to agree with that as well. Which is what makes the surge so foolish -- why embark on an unsustainable course of action? Certainly it's what makes talk of the surge's success so foolish. The goal, after all, was to put Iraq on a sustainable path. But the surge force levels aren't sustainable. And the security gains are unlikely to be sustainable if we move our force levels to a sustainable level.

That's not "external politics" meddling with a solid plan, it's reality crashing down.

DoD photo by Mass Communication Specialist 1st Class Sean Mulligan, U.S. Navy