Chang Hsien-yi

Colonel Chang did not return to Taiwan from a holiday on 9 January 1988, and instead coerced his family to defect with him to the United States. Chang brought with him numerous top-secret documents that could not have been obtained by other means, though an article from the BBC claims Chang did not take a single document. A study into the secret program concluded that at the time of Chang's defection, Taiwan was one or two years away from being able to complete a nuclear bomb. According to The Economist, there were plans to fit nuclear warheads to Taiwan's Tien Ma, or 'Sky Horse' missile, which had an estimated range of up to 1,000 kilometres. There were also plans to load miniaturised nuclear weapons into the auxiliary fuel tanks of the Indigenous Defense Fighter. Armed with Chang's documents, President Reagan insisted that Taiwan shut down its program.

Taiwan uses nuclear power for some of its electricity generation, but since 1988, its official position has been that it will not develop nuclear weapons. Were it to do so, China has said it would be 'a legitimate reason' to launch an attack on the island.

Taiwan's Ministry of Defence denied that Chang had been a CIA informant. Its retired Chief of General Staff (1981-1989), General Hau Pei-tsun, claimed that for more than a decade previously, Taiwan already had the potential to develop nuclear weapons. A former member of President Lee Teng-hui's national security team, Chang Jung-feng, has described Chang's actions as a 'betrayal'. The CIA has refused to discuss Chang's defection. James R. Lilley, who served as CIA station chief in Beijing, said the case should be 'publicly acknowledged as a success'.

In 1967, Chang graduated from the military's Chung Cheng Institute of Technology (now National Defense University). Then from the 1970s, he was recruited by a case officer of the CIA while studying in America. While rising through the ranks in Taiwan, he passed on information to the USA. By 1987, as Deputy Director of INER, he was well-positioned to provide information about the country's secret small-scale plutonium extraction facility. At this time, the Reagan administration considered it possible that the secret program was proceeding without the knowledge of Taiwan's president Lee Teng-hui.

Chang Hsien-yi (Chinese: 張憲義; born 1943) served as deputy director of Taiwan's Institute of Nuclear Energy Research (INER) before defecting to the United States of America in 1988. Recruited by the CIA, he exposed the secret nuclear program of Taiwan to the United States and was consequently placed under witness protection. Chang's information led President Ronald Reagan to insist that Taiwan shut down its nuclear weapons program.

Chang was born in 1943 in Haikou City, Hainan, with Taiwanese parents. He went to Taichung Second National High School, and attended National Tsing Hua University, where he obtained a Bachelor of Science degree.