AP Photo

Why is Afghanistan so hard? It's not difficult to think of reasons: 1) the long-standing divisions among the various tribal/ethnic groups that make up Afghan society, 2) the mountainous, inhospitable terrain, 3) lack of infrastructure, 4) weak governmental institutions and little history of centralized authority, 5) the destructive effects of many years of warfare, 6) endemic corruption, 7) traditional hostility to foreign occupation, etc. ... Given all that, it is hardly surprising that outside efforts to rebuild the country and establish a legitimate central government have thus far failed to accomplish very much.

If that weren't enough, our efforts there are also hampered by some inherent strategic contradictions. In particular, most of the things the United States might do...