The president said yesterday that he's asking new Defense Secretary Gates to tell him how many more troops should be sent to Iraq. Gates is in Iraq now, meeting with senior commanders and, presumably, going out in the field to see things for himself. In the wind is a three to six-month "surge" of troops to Iraq. A few key questions need to be asked before we send anyone more to Iraq.

First is what will they do when they get there? Some pundits think we're going to "take the gloves off", destroy the militias and somehow - by house to house fighting if no other way - rout the insurgents of all stripes to give the Iraqi government breathing room in which to accomplish their political compromises and sing a chorus or two of "Kumbaya." None of this is remotely possible.

First, if we are temporarily deploying more forces we are necessarily telling the insurgents to fade away, take their money, weapons and key people underground, and wait us out. They can evade us and wait us out. It's almost as bad as announcing a firm date for withdrawal of all Americans. We are in a very tough spot because some military leaders have said publicly - in Congressional hearings and elsewhere - that we lack the forces to support a sustained effort in Iraq much longer. The enemies watch those hearings more closely than Americans do.

Second, the Maliki government is so terribly weak, and so dependent on the support of thugs such as Moqtada al-Sadr, that it will not permit us to do what should be done to destroy the Shia militias and the Sunni insurgents. If we choose to operate regardless of Maliki's limitations, his government and the Iraqi constitution would be nullities. We'd be back where we were in 2003. Which may not be entirely a bad thing. If Maliki fell without taking the Iraqi constitution with him, a stronger coalition government has a chance to arise. Now, one does not.

Third, without a clear military mission for the increased forces, we may - by default - start ordering them to perform routine street patrols that had been patrolled recently by Iraqis. They will be little more than moving targets for snipers and IEDs. The success of such local patrols depends on time on the streets: the more you have, the more the people learn to trust you, not fear you, and the more success you have in learning who is the good guy and who isn't. Our soldiers aren't policemen. And to train them to be police, we untrain them for their primary combat role. They can't be both.

We can "send a message" by sending more troops temporarily. But it's not the message that we are determined to win this war. Mission and strategy are what troops are to perform. Not nation-building or sending diplomatic signals.