Sometimes leaning back will allow interventions to occur without any American troops on the ground. This is because of the interesting, counterintuitive property of the lean-back concept: The reduced U.S. military presence both ends the "free ride" (as Posen puts it) that allies have enjoyed and makes their forces more effective with a little leavening of American logistics, intelligence support, and drone strikes. This approach is working well for French and Malian forces right now; they are driving Islamist rebels before them, soon right out of northern Mali. Earlier, this lean-back approach worked in Libya as well, and it is clearly the strategic tack being taken in the Syrian conflict. Interventions of this sort are preferable to, say, the Iraq model, where over a trillion dollars were expended, tens of thousands of American lives were lost or shattered, and, now that we have left, al Qaeda is back and an Iran-friendly government holds power.
The beauty of leaning back is that it completely scales down the cost structure of American foreign policy and security strategy -- but it does so in a way that allows not only continued but possibly even expanded international engagement. My long-time research partner at the RAND Corporation, David Ronfeldt, sees matters this way: We can be both scaled-down and "scaled out" -- that is, more widely deployed. Back in 1999, we recommended such an approach be taken during the Kosovo War, by adding a few of our at-the-ready Special Forces teams to the fighters of the Kosovo Liberation Army. The choice was made not to do so in that particular war, but two years later our initial operations in Afghanistan, limited to about 200 Special Forces soldiers on the ground, won a stunning victory with this approach. It is a mode of operation that can be applied almost anywhere in the world, a point that should assuage the concerns about disengagement raised by Brooks, Ikenberry, and Wohlforth.
The truth of the matter is that we cannot afford to continue the longstanding Powell doctrine that calls for the employment of "overwhelming force" in our interventions. Besides, massive numbers and huge firepower failed in Vietnam, and efforts to "overwhelm" had very mixed results in Iraq and Afghanistan. But the end of overwhelming force does not require withdrawal from the world. There is now the option of deploying smaller, more precision-oriented units, enabling the United States to remain actively engaged wherever its interests and/or moral impulses demand. There is no need to pull back, and there is a way to avoid the undue costs that come with just leaning forward in the usual way. This new way is the path of "leaning back." President Obama is sometimes criticized for being too cool, but in the strategy business he knows enough to lean back. A commander-in-chief can never be too cool.