China has one of the largest and most consequential militaries in the world, but how Beijing thinks about its military and makes military decisions is largely a mystery to the outside world. The People's Liberation Army is technically attached to the Chinese Communist Party, rather than to the Chinese government, and scholars often describe it as a "black box" because it is so difficult to understand from the outside.

Last week's decision by China to impose a special air defense identification zone over international waters was one such mystery. China announced that any foreign flights into the ADIZ would have to alert Beijing first and file a formal flight plan. The outcome was entirely predictable: The United States immediately violated China's requirement by flying two unarmed B-52 bombers into the zone, basically a way of announcing that the U.S. would ignore China's requirement. Japan and South Korea also sent in flights. China's ADIZ not only failed, it backfired, embarrassing China while further uniting Japan, South Korea and the U.S. against Chinese military assertiveness.

So why did China do it? Why impose an air defense zone that was so likely to fail in its most apparent goal of enforcing greater Chinese control over nearby international waters?