I think Matt misses the truly insidious follow through of this:
I’ve been struck over the past three or four years by how many different Chinese people have expressed to me the view that the purpose of U.S. military engagement in Afghanistan is to establish a long-term presence there in order to encircle the PRC. This would not, as a policy objective, make much sense, but I think it does illustrate the important fact that Chinese people have a China-centric view of the world.
If you want to see how foreign policy commitments metastasize, think this through: If the Chinese believe that the United States is in Afghanistan in order to encircle China (and to be sure, I don’t think this), then a US withdrawal from Afghanistan becomes a “win” for China, even if Chinese beliefs were without foundation. If the Chinese believe that the American encirclement project has failed, then they might be inclined to take more aggressive steps in some other part of the world that touches on “genuine” US national security interests.
And thus, we need to stay in Afghanistan in order to make the Chinese believe that we’re committed to the encirclement project, even if we’re not interested in the encirclement project. It’s right there in the Schelling, and Kissinger would totally understand.