On september 25, 1992, china tested a new type of nuclear bomb. For the next several years, analysts and scientists in the United States studied data on the test; in time, scientists at the Los Alamos nuclear labs, where the first U.S. nuclear weapons had been developed, became worried that the test showed that the Chinese were developing dramatically smaller warheads. If true, this represented a dramatic potential increase in China's nuclear capabilities. Miniaturized warheads could go on mobile missiles that would be harder to detect, and eventually they could be used as multiple warheads on strategic intercontinental missiles. The scientists were concerned that the Chinese could only have made such progress if they had based their warhead designs, in part, on nuclear weapons technology stolen from the United States. These fears appeared to be confirmed by a 1995 Central Intelligence Agency (CIA) report, based on 1988 documents, stating that the new Chinese bomb was similar to American technology.

Counterespionage investigations are among the most daunting challenges for intelligence analysts. It can be difficult to determine for certain, especially over the short term, whether espionage has even taken place. Spies are often experienced professionals who know how to cover their tracks. Even if there are well-founded suspicions, coming up with evidence that can hold up in court can be demanding. In any case, the investigation is almost certain to require considerable amounts of time, money, and expertise, with an uncertain outcome.