The Official History is as follows: The neutron bomb is generally credited to Samuel Cohen of the Lawrence Livermore National Laboratory, who developed the concept in 1958. Although initially opposed by President John F. Kennedy, its testing was authorized and carried out in 1963 at an underground Nevada test facility. Development was subsequently canceled by President Jimmy Carter in 1978, but again restarted by President Ronald Reagan in 1981. Three types were built by the United States. The W66 warhead for the anti-ICBM Sprint missile system was produced and deployed in the mid 70s and retired soon thereafter along with the missile system. The W70 Mod 3 warhead was developed for the short-range, tactical Lance missile, and the W79 Mod 0 was developed for artillery shells. The latter two types were retired by President George Bush (Senior) in 1992 due to the end of the Cold War. The last W70 Mod 3 warhead was dismantled in 1996, and the last remaining neutron bomb (W79 Mod 0) was dismantled by 2003 when the dismantling of all W79 variants was completed. France tested a neutron bomb at the Mururoa Atoll on June 24, 1980. Enhanced radiation weapons were also produced by France in the early 1980s, though they have since destroyed these weapons. The 1999 "Cox Report" indicates that China is able to produce neutron bombs, although no country is known to currently deploy them. * * * * * * Unofficially ??? I suspect (this is to say it is my opinion) that the N Bomb was developed and was built and IS kept along with Thermo-nukes. Simply because it is a logical type bomb, one that kills people and leaves cities, military bases, warehoused goods in tact and still useful. It is a strategic type weapon, one that would be very useful in a small exchange of weapons fire. Unlike the H Bomb which leaves a lot of rubble, a crater and a radioactive footprint for thousands of years, the N bomb is a "clean" weapon that leaves the bombed place habitable in a very sort time (less than a month). The USSR most likely did develop and build many of these type bombs, since it was not just planing on bombing the world to ash, but maintained a serious program of taking over the whole world.