In its continuing search for an alternative to General Stanley McChrystal's comprehensive counterinsurgency approach to the war in Afghanistan, and with President Obama having eliminated the minimalist counterterrorism plan of Vice President Joe Biden, the White House has lately been floating a split-the-difference trial balloon: "McChrystal Lite" or, to give the veep his due, "McChrystal for the cities, Biden for the countryside."

Last week the New York Times was allowed a sneak-peak of what this half-pregnant approach might look like. It reported that White House advisers are aiming to defend "about 10 top population centers." A number of press accounts indicate that the number of additional troops would be capped at around 20,000--half the 40,000 recommended by McChrystal--no more than four brigade-sized units and the needed support. The Times also indicated that McChrystal had briefed the White House on how he would employ any reinforcements: "The first two additional brigades would be sent to the south, including one to Kandahar, while a third would be sent to eastern Afghanistan and a fourth would be used flexibly across the nation."

To the Washington punditocracy, half a loaf sounds about right; even if they don't think it's the right strategy, they think it's what Obama will do as a matter of domestic politics. But does it make any military sense?

A troop ceiling of 20,000 reinforcements would present McChrystal with painful choices. To begin with, it would sacrifice urgency, taking longer to achieve any decisive effects--and McChrystal's assessment concluded in August that the coming year was critical. The president's middle-way approach would also force McChrystal to revisit the balance between committing U.S. troops to combat and to training Afghan Army and other security forces; and he might have to reconsider the trade-offs between formal school-house training, embedded training teams, and unit-to-unit partnerships, the approach that proved to be most effective in Iraq. But even if he were to maximize the combat punch of half a surge, he would face challenges in deploying the new forces. Consider these possible courses of action:

McChrystal's planned deployment of additional forces as described in the Times represents a sensible effort on the part of the general to prioritize the most violently contested areas of the country and address them as effectively as possible. Nevertheless, the "two south, one east, one in reserve" disposition would force McChrystal to accept a great deal of risk by spreading the force thin and failing to achieve adequate counterinsurgent-to-population ratios, as a recent study by Frederick and Kimberly Kagan, based on their many trips to the region, makes plain (see

Let's begin with the "two south" slice of this plan. Southern Afghanistan remains the heartland of the insurgency, and it is widely understood that Kandahar City and the surrounding districts of Kandahar Province are the Taliban's center of gravity. The Kagans calculate the U.S., Canadian, and Afghan troops already deployed around the city to be a force of 4,800, which is responsible for maintaining security among a population of 1,015,000. The counterinsurgent-to-population ratio, then, is one to more than 200, or less than a quarter what counterinsurgency doctrine dictates. Unlike Iraqis, Afghans--including the Taliban--traditionally prefer to avoid fighting in their cities. Even so, security in the city is essential, and at the moment only Afghan National Security Forces conduct patrols there, making the ratio inside the city even less favorable. Even if both of the brigades McChrystal intends to send to the south were deployed to the Kandahar City area, they would not improve the counterinsurgent-to-population ratio there enough to have a decisive impact. The Kagans' detailed study estimates that it would take roughly four and a half brigades to reach the desired ratio. It's also worth noting that the Canadians will be withdrawing their forces by mid-2011; if the area is not secure by then, their departure will create a larger gap.

Placing both of the new brigades destined for the south in Kandahar, moreover, would shortchange Helmand Province, nextdoor, where the Marines, British, and Danes have made substantial progress in recent months. Military operations there are complicated by the fact that Helmand is the center of the poppy production that feeds the opium industry which helps to finance the Taliban and corrupt the Afghan government. By putting one brigade in Helmand and one in Kandahar, McChrystal could likely consolidate and expand gains in Helmand, where the current troop-to-population ratio in the contested river valley is a reasonable 1:83 (though even with an additional brigade it would fall short of the 1:50 ideal). This would also have the benefit of consolidating the political partnership with Great Britain and Denmark--the two NATO allies most committed to staying the course in Afghanistan. Conversely, it would further shortchange Kandahar, which is a greater strategic priority.

The third brigade-sized unit, meanwhile, would be deployed among the volatile eastern provinces of Paktia, Paktika, and Khost--better known as Greater Paktia--where the combined strength of U.S. and Afghan forces is 8,200 and the force ratio is 1:79. The region is critical in many ways. The western parts sit astride the key Kabul-to-Kandahar highway, and the bowl-like area around Khost is just across the border from North Waziristan, the sanctuary of the Haqqani network, a Taliban-affiliated militia that operates in Afghanistan. The additional brigade in this region would make a big difference, not only consolidating recent gains but no doubt improving prospects for counterterrorism strikes against the Haqqanis, the younger of whom, Sirajuddin, is both a charismatic leader and highly radicalized.

The mission of the "reserve" brigade is less clear, although it is true that forces in Afghanistan have been stretched so thin that senior commanders have essentially been without a significant tactical or operational reserve with which to shape or react to events. But a reserve brigade is one thing in the context of a "Full McChrystal" surge of eight brigades and quite another in the context of a half-surge. First of all, under McChrystal Lite, chances are it wouldn't be in reserve for long. It would be far more likely to be committed, or tied down, as the result of having to react to an insufficient level of force across the theater; that is to say, it would more likely be used to prevent failure than to reinforce success. And there would likely be a temptation to parcel it out piecemeal around the country, lessening its impact and making it harder to support and sustain.

But this sequence of deployments--the one leaked to the Times--is surely a derivation from the sequence planned for the full complement of forces that McChrystal requested. Once he faces the reality of a cap on the troops available, McChrystal may rearrange the deck chairs. In particular, he may decide to mass all of the forthcoming brigades in the area that's most strategically vital and presents the greatest security challenge: Kandahar. Then there will be questions as to how best to balance the forces within the province between those focused on securing Kandahar City and those disrupting rural insurgent sanctuaries and lines of communication in the surrounding province.

But there's a very strong argument for a Kandahar-centric surge. Not only is Kandahar the Taliban's strategic center of gravity, but the key area of operations--those parts of the province that are contested--is the largest and most populous "battle space" in southern Afghanistan. Beyond the city-focused forces described above, there are now about 7,200 U.S. and Afghan forces deployed in the province. Three additional brigades in the Kandahar City area would very nearly provide the number of troops necessary to conduct a proper counterinsurgency mission; another brigade elsewhere in the northern portion of the province would help provide those focused on the city with increased room to breathe and strategic space in which to operate.

The downside of this approach, of course, is its opportunity costs: Decisive action in Kandahar precludes decisive action elsewhere. Helmand and the volatile provinces in the east would be left to fend for themselves until the operations in Kandahar were complete. There would likely be few demonstrable regional synergies in the short term, either--the Kandahar "ink spot" would not be linked to any other save that created by the new rurally focused brigade in Kandahar, which could presumably provide support to the population center of Tarin Kowt, north of Kandahar in Oruzgan province. But since the Dutch battalion in Oruzgan is scheduled to leave next year, larger or longer-term local success would be uncertain. Nevertheless, an all-in approach to Kandahar would have good prospects for achieving at least a localized example--and arguably the most decisive example--of sustainable security.

This would be, to force an Iraq analogy, akin to having succeeded only in Anbar in 2007, without the follow-on successes in the Baghdad belt, in the capital, in Basra, and in chasing al Qaeda and the insurgents northward. So even if an incomplete surge could chalk up some successes, other risks would continue to rise. Violence has long been festering in northern Afghanistan, with the Taliban resurgent there and election tensions accelerating the trend; Kunduz and Mazar-e-sharif are on the White House "Top 10" list of cities to be secured, but it's hard to see how, with a semi-surge, anything more could be done there. Likewise, in the west, Herat is critical but has been all but neglected heretofore.

Officers in Afghanistan ruefully observe that you can't have an ink-spot strategy without enough ink. A half-surge would increase the amount of ink, but Afghanistan is a large and dry piece of paper; McChrystal Lite would make it hard to connect the dots. It would also be hard to synchronize the effort with the nascent counterinsurgency campaign in Pakistan. It's good news that the Pakistani Army is pushing into South Waziristan, but unless there is pressure across the border in Khost and greater Paktia, the likelihood of Pakistan advancing against the Haqqanis is negligible.

The biggest problem, though, is that a half-surge cannot produce a meaningful result in a timely manner; we should remember that the McChrystal plan proceeds from his assessment that the next year--several months of which have already been lost--is critical to regaining the initiative from the Taliban.

Time matters not only in Afghanistan, but also in Pakistan and, most of all, in Washington and across America where, absent some sign that the war can be won, political and public support is increasingly shaky. If McChrystal Lite is problematic from a battlefield perspective, it's worse from a strategic and political standpoint.

A clever commander like McChrystal and the capable troops he leads will no doubt figure out how to make the most of what they've got. But a half-surge would seem to cut their prospects of winning by more than half.

Tom Donnelly is the director of the American Enterprise Institute's Center for Defense Studies. Tim Sullivan is the Center's program manager and a research fellow at AEI.

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