As has become the case with other topics of importance, the most intelligent discussion of troop strength in Iraq is to be found in the blogosphere. For instance, the incomparable Belmont Club has an extensive three-part discussion with numerous links and readers’ comments. The entire conversation runs to nearly 100 pages.

There are several reasons that the mantra of "not enough troops in Iraq" is misleading. Two stand out. The first is we have committed all the troops to Iraq that we can. As Kevin Drum recently observed, if the United States were to strip every soldier and Marine from other tasks and utilize every possible National Guard and reserve brigade, it could conceivably provide 500,000 troops for duty in Iraq. Of course, this is unrealistic. So the fact is that "the maximum number of troops available for use in Iraq is probably pretty close to the number we have now: 300,000 rotated annually, for a presence of about 150,000 at any given time."

Well, why not increase the size of the Army, as called for by the Senate Democrats? There are some good reasons for doing so, but action taken today will not have an impact on current operations in Iraq. Even if the Army moved today to increase the number of its combat brigades, it would be unreasonable to expect them to be ready in less than two years.

Kagan takes Rumsfeld to task for not expanding U.S. ground forces immediately after taking office. But had Rumsfeld in 2002 used an impending strike against Iraq as his rationale for expanding the Army, he would have made the war, which Kagan and Sullivan supported, politically impossible. "The invasion of Iraq," argues Drum, "almost certainly would never have happened if Rumsfeld had told Congress in 2002 that he wanted them to approve three or four (or more) new divisions in preparation for a war in 2004 or 2005. In other words, when Rumsfeld commented that you go to war ’with the army you have,’ he was exactly right."

We also need to remember that the Iraq invasion did in fact call for a larger force than was initially employed. But Turkey did not permit the opening of a northern front by the 4th Infantry Division, the attack of which through the Sunni Triangle may have changed things on the ground.

The second reason for rejecting the argument that the cause of problems in Iraq is simply a function of a lack of troops is that success in war, guerrilla or otherwise, is not simply a function of numbers. For instance, critics of the American conduct of the war argue that "traditional military doctrine" says a ten-to-one force ratio is necessary to defeat an insurgency. But this suggests that all insurgencies are the same. They are not.

Operational considerations differ from conflict to conflict and depend on a number of factors that are difficult to quantify. How strong are the insurgents? Do they have popular support? What kind of organization do they have? What is their source of supply? What is the quality of guerrilla leadership? What is the character of the terrain? What are their tactics? Answers to these questions should drive force levels, organization, and tactics. As I argued in an earlier piece criticizing the penchant of so many commentators to equate Iraq and Vietnam, Iraqi guerrillas lack many of the advantages that have fueled successful insurgencies in the past.

One of the points I made is that guerillas traditionally have been most successful when they serve as an auxiliary to a "force in being," a conventional military formation that concentrates the main effort of their enemy. After all, the term "guerrilla" was first used to describe the Spanish partisans who, in conjunction with a British force, harried Napoleon’s army during operations in Spain in 1810. The guerrillas were effective only because the French had to focus on Wellington’s army. Because they always had to contend with the British main force, they could not organize their forces in such a way as to pursue and kill the guerrillas. That is essentially what the Viet Cong guerrillas did in Vietnam as well. But the guerrillas in Iraq are on their own. This means that we can optimize our force structure for counter-guerrilla operations.

The key to success in Iraq is killing or capturing the guerrillas. We have had substantial success in doing so in such places as Fallujah and Ramadi. But while we have plenty of conventional military firepower in Iraq—enough to kill the guerrillas many times over—we often lack actionable intelligence. It is intelligence that indicates what targets must be struck or safe houses raided. This is the real constraint we face today in Iraq.

And it is no doubt one of the reasons that Secretary of Defense Rumsfeld has dispatched retired Army general Gary Luck to review U.S. strategy in Iraq. If we are to believe Newsweek, one of the alternatives now being considered by the Pentagon is something the media have breathlessly dubbed the "El Salvador Option." According to Newsweek,

the Pentagon is intensively debating an option that dates back to a still-secret strategy in the Reagan administration’s battle against the leftist guerrilla insurgency in El Salvador in the early 1980s. Then, faced with a losing war against Salvadoran rebels, the U.S. government funded or supported "nationalist" forces that allegedly included so-called death squads directed to hunt down and kill rebel leaders and sympathizers. Eventually the insurgency was quelled, and many U.S. conservatives consider the policy to have been a success—despite the deaths of innocent civilians and the subsequent Iran-Contra arms-for-hostages scandal.

The fact is that such an approach may be one of the most effective ways to destroy an insurgency. Consider the even more controversial Phoenix Program of Vietnam War fame (or infamy). This approach used South Vietnamese agents, trained by U.S. military personnel, to penetrate Vietcong operations in the South and arrest or kill Communist cadres. According to Stanley Karnow, certainly no fan of the war, the Phoenix Program almost wrecked the Communist infrastructure in South Vietnam. As Karnow writes in Vietnam: A History,

…I was inclined to discount the claim advanced during the war by William Colby, the CIA executive who ran Phoenix, that the endeavor as a whole, despite it flaws and excesses, eliminated some sixty thousand authentic Vietcong agents. My perspective changed after the war, however, when top Communist figures in Vietnam confirmed Colby’s assessments. Madame Nguyen Thi Dinh, a veteran Vietcong leader, told me that Phoenix had been "very dangerous," adding: "We never feared a division of troops, but the infiltration of a couple of guys into our ranks created tremendous difficulties for us." Ro Colonel Bui Tin, a senior officer, it had been a "devious and cruel" operation that cost "the loss of thousands of our cadres," and the deputy Communist commander in the south at the time, General Tran Do, called it extremely destructive." Nguyen Co Thach, Vietnam’s foreign minister after 1975, admitted that the Phoenix effort "wiped out many of our bases" in South Vietnam, compelling numbers of North Vietnamese and Vietcong troops to retreat to sanctuaries in Cambodia.

Having the right approach is more important than raw numbers of troops. Success in war depends a great deal on what those troops are doing. In a guerrilla war, a smaller force on the offensive is more likely to achieve success than a far larger one that is in a defensive posture. Phoenix II would enhance our offensive orientation.

Mackubin Thomas Owens is an associate dean of academics and professor of national-security affairs at the Naval War College in Newport, R.I. He led a Marine rifle platoon in Vietnam in 1968-69.