Assume, as most but not all people do, that the American commitment in Iraq cannot and should not be sustained indefinitely whatever happens. What should the American military be doing there in the meantime?

I'd like to think that if I were lugging a rifle and a pack around Baghdad in the middle of the night my mission would be something a little more specific than "staying the course," "showing resolve," and "spreading freedom." Marking time until the Iraqis "stand up" seems somehow inadequate as well. What should our military's objective be in its operations in Iraq right now?

There is nothing original or even very clever in my idea that priority No. 1 should be to increase tensions between Iraqi Sunni Arabs and non-Iraqi jihadis. We know these tensions exist. We see evidence of them popping up occasionally in the mainstream media and in the Iraqi section of the blogosphere. To some extent they supply the answer to a question I asked last spring:

"...what is the likely impact of (apparently) widely divergent objectives on the part of different groups of insurgents on the future of the insurgency?"

Sunni Arab Iraqis may be fighting to avenge perceived humiliation, to restore Sunni political domination of Iraq or because they have nothing else to do, but they aren't fighting to become subjects of Saudi clerics and Jordanian professional terrorists -- and the foreign jihadis in turn are not fighting and dying just to uphold the honor of local tribal leaders or to restore a secular Baathist regime. They have had a common enemy, but no common goals.

Does this situation present some opportunities for us? Well, it ought to. But the difficulties are very considerable. Intelligence assets needed to identify exploitable areas of tension are evidently limited. This has to be partly because the enemy is aware of potential tensions between Iraqi and other fighters and is taking steps to keep them under control, and the uncertain political situation may be another reason. Probably the biggest, actually, is the thing that has plagued American intelligence since March 2003: the language barrier. In any event the desirability of encouraging "red-on-red" hostility is much clearer than are the things we need to do this.

In fairness to the many journalists, bloggers and others now arguing fiercely about levels of commitment, withdrawal timetables and so forth, these are much easier to grasp than are the tactical issues. It is easy enough to sit here on the East Coast and advise attempting to disengage from insurgents in areas where these are known to be entirely Iraqi while seeking out non-Iraqi fighters to attack; identifying likely gathering points on the insurgent "rat line" across the Syrian border and striking them from the air; or leaning on the Iraqi government to make sure that the non-Iraqi jihadis they capture never make it home. Whether any of these things is practicable I do not know. It is, again, easy to advise an offensive posture -- sitting around or patrolling up and down the same roads waiting to be attacked is neither good for morale nor likely to lead to a won war. Implementing this advice is easier said than done.

The other question I asked last spring was:

"...at what point does the enthusiasm of some Sunnis for massacring Shiites become a factor in our relations with Iran?"

I'm inclined to think now that this train left the station long before I posed this question. Iraqi Shiite leaders who did not fear assassination or massacres of their followers were much less likely to submit to Iranian influence than the ones we have now. Zarqawi and his followers have their own reasons for murdering Shiites Muslims in large numbers; Sunni Arab Baathists do too, and while these reasons may not be the same they do seem to have been compatible to this point (what appears to be the rather short moral distance between the most dedicated Baathist and the most zealous Wahhabi is probably a large obstacle to any plan to divide the two). Shiites seeking protection from terrorism will not rely on the American military; they know the mullahs in Tehran will want to fight their enemies, and know the Iranians will be there long after the Americans are gone.

There is a limit to how much we can do to limit Iranian influence in Iraq under these conditions. Actually, we may have been lucky -- if that idiot Muqtada Sadr hadn't thrown away many hundreds of his best men in frontal confrontations with American main force units last year we might already have a full scale Shiite/Sunni war in Iraq. In any event we share some interest with secular Shiite leaders and some Shiite clerics in avoiding a situation where a future Iraqi government becomes dependent for its survival on Iranian support, giving us, perhaps, another potential partner in an effort to separate our Iraqi enemies from our Islamist ones.