OVERVIEW: The Type 639-6 is a strategic thermonuclear gravity bomb developed by China, believed to be one of the most powerful nuclear bombs in its arsenal.

DETAIL: Developed in the late 1970s or early 1980s, the Type 639-6 represents a continuation of China's strategic bomb program, possibly derived from enhanced thermonuclear designs tested after its successful 1967 hydrogen bomb. It is believed to be based on or related to the warhead design of later-generation DF-series ballistic missiles. The weapon is likely fitted with a two-stage Teller–Ulam configuration using boosted fission primaries and thermonuclear secondaries.

Due to its high yield, the bomb was designed for countervalue or counterforce missions, capable of destroying hardened command infrastructure or large urban centers. Its size and weight would have required deployment from heavy bombers such as modified versions of the Xian H-6. Limited information exists on its physical configuration, but it likely retained conventional aerodynamic shaping and may have included safety interlocks and arming delays for in-flight deployment.

Operational history is uncertain, but the Type 639-6 was likely retained as part of China’s strategic deterrent into the late Cold War era. It may have been gradually phased out in favor of missile-based delivery systems with faster response times and greater survivability.

NOTE:
IOC: ~1980s
Operators: China (People’s Liberation Army Air Force)
Platform: Xian H-6 (nuclear-capable variant)
Conflicts: None (strategic deterrent posture only)

SOURCE:
Federation of American Scientists (FAS) ; Bulletin of the Atomic Scientists ; Chinese Nuclear Forces, NRDC/Carnegie Endowment ; Jane’s Nuclear, Biological and Chemical Defense ; U.S. Department of Defense, Nuclear Posture Review https://www.fas.org/nuke/guide/china/nuke/index.html ; https://thebulletin.org ; https://carnegieendowment.org ; https://www.janes.com