From the Benge Report: Cuban officials, under diplomatic cover in Hanoi during the Vietnam War, brutally tortured and killed American POWs whom they beat senseless in a research program "sanctioned by the North Vietnamese."(1)
This was dubbed the "Cuba Program" by the Department of Defense (DOD) and the CIA, and it involved 19 American POWs (some reposts state 20). Recent declassified secret CIA and DOD intelligence documents, obtained under the Freedom of Information Act, reveal the extent of Cuba's involvement with American POWs captured in Vietnam. A Defense Intelligence Agency (DIA) report states that "The objective of the interrogators was to obtain the total submission of the prisoners..."(2)
According to former POW Air Force Colonel Donald "Digger" Odell, "two POWs left behind in the camp were 'broken' but alive when he and other prisoners were released [1973 Operation Homecoming].* ... They were too severely tortured by Cuban interrogators" to be released. The Vietnamese didn't want the world to see what they had done to them."(3)POWs released during "Operation Homecoming" in 1973 "were told not to talk about third-country interrogations. .... This thing is very sensitive with all kinds of diplomatic ramifications."(4) Hence, the torture and murder of American POWs by the Cubans was swept under the rug by the U.S. Government.
*KPOWS note: the bodies of these two men were returned by Vietnam after the war. There are also indications Havana may know about other American POWs who disappeared during the war -- see details in the report.