The detention of a Chinese spy in Belgium, and his transfer to U.S. custody this week, is a landmark victory for the FBI and the U.S. intelligence community. Still, that spy won't likely spend long in U.S. prison. He'll probably be traded for U.S. spies in Chinese custody.

As reported by the Washington Post, Yanjun Xu of China's Ministry of State Security intelligence service, was detained in Belgium after believing he was traveling to meet a U.S. supplier of aviation-related technologies. Unfortunately for Xu, he was meeting with the FBI, which had engaged in a classic "dangle" operation. Xu has now been indicted in federal court for a number of espionage-related charges.

But Xu is likely to be heading home within one or two years. That's because the spy has far more trade value than he does intelligence value. As a quite senior member of the MSS, Xu knows full well that his cooperation with U.S. authorities would greatly endanger his life if he ever returns to China. That would have naturally inclined him to stay quiet. Moreover, the fact that the U.S. government has unsealed the indictment against Xu suggests that he has refused to cooperate. Had he chosen otherwise, the indictment would have stayed sealed, and Xu eventually put back into play as a double agent for the U.S. on Chinese soil. Yet in Xu, the U.S. now has an important bargaining chip with which to earn the release of Chinese-held prisoners.

That value is very important for America. After all, the U.S. wants to show its global agents — those working for a foreign government or group who covertly provide intelligence to the U.S. — that they won't be forgotten even if caught. This is not so much of a moral mission as it is an intelligence strategy. Consider that if person X spying in country Y for country Z knows that country Z will try to extricate them if they are ever caught, person X will have better reason to keep spying in country Y. This is an especially significant concern in China, which is a very high priority U.S. intelligence target but also a place where spies are hard to recruit and hard to retain (the Chinese invest massive efforts in trying to track down American agents).

So, yes, Xu will likely be heading home soon enough. But if that happens, his return won't be a defeat for the U.S.; rather, it will be the price tag for a greater American success.