Now for a closer look at the specific details Snowden turned over. In trying to understand this, I reached out to an individual I know who spent much of a lifetime in the intelligence world, including some related to parts of Asia. While he specifically stated that nothing he discussed would be based on classified information, he was able to offer a number of educated explanations why the United States would be involved in the activities in China that Snowden revealed.

Take the actions involving Tsinghua University. There are many reasons the N.S.A. would be interested in communications and computer activities at this Beijing-based school. For example, beginning in the past decade or so, university programs on arms control have played an important role in the Chinese government’s efforts to administer export controls on sensitive items. (For those wishing to know more, this is well detailed in a book published by the Rand Corporation called Chasing the Dragon: Assessing China’s System of Export Controls for WMD-Related Goods and Technologies.) Now, perhaps the most prominent university program in China on arms control is at—you guessed it—Tsinghua University. So, do you think there might be a reason why the N.S.A. would want to know about any communications on arms control that might take place between the Chinese government and Tsinghua?

The importance of China in global arms-control issues is hard to understate, even in American negotiations with Russia over proposals on nuclear-arms reduction.