Military Intelligence Corps

After the war, Cumby was assigned intelligence duties and played an important role during the Korean War in the debriefing of returning American prisoners of war (POWs) following Operation Big Switch. He was later called before the United States Senate to answer questions of alleged communist indoctrination of American POWs, during which he testified to the Permanent Subcommittee on Investigations that roughly one-third of all American POWs had collaborated "to some degree" with their North Korean and Chinese captors, often due to thought reform overseen by officers of the Soviet Army as part of an international communist conspiracy. According to Cumby, POWs were required to attend a series of twelve classes on Marxism–Leninism, while coursework beyond the twelfth lecture was voluntary. Those prisoners who elected to continue instruction were identified as a "core" element for the alleged indoctrination regime.^[1][5][6] Cumby also testified that, based on his analysis of the curricula of the advanced courses, he had concluded that the ultimate strategic vision of the People's Republic of China was to assume China's seat in the United Nations and to establish diplomatic relations with the United States.^{[5][lower-alpha 1]} Cumby alleged that the pre-repatriation indoctrination of American POWs was intended to create a nucleus of post-war civilians who would advocate in the United States for these objectives.^[5]

Cumby was among the interrogators of Claude Batchelor.^[5] He also provided testimony for the prosecution in the trial of a former POW for collaboration; to protect his identity he appeared in court with his face concealed and was referred to only as "Mr. X".^[9][10]

Later in his career he was an instructor at the United States Army Intelligence Center and served as head of research for the Military Intelligence Corps.^[1]

U.S. Foreign Service

Cumby retired from the U.S. Army in 1961 at the rank of lieutenant colonel and entered the United States Foreign Service, holding overseas postings in Thailand and Spain.^[1]

Family

Cumby was married. With his wife, Esther, he had one biological son and also adopted an adolescent boy from Luxembourg, the adoption facilitated by the socialite and United States Ambassador to Luxembourg Perle Mesta.^[11][1]

Esther Cumby was a high school classmate of Agatha Davis, the wife of General Benjamin O. Davis Jr.; in his autobiography, Benjamin Davis described Bert Cumby as "a good friend".^[12] Esther Cumby, a third generation New Englander, was a schoolteacher by profession.^[13] Early in her career she volunteered to teach in a segregated school. According to Cumby, upon accepting the assignment, she "knew practically nothing of the separate schools for Negroes" and had volunteered "not because of any great race consciousness ... but because the pay scale was more attractive".^[13]

Retirement and death

Following his final retirement, Cumby remained active with the Association of Former Intelligence Officers.^[14] A resident of Silver Spring, Maryland, in 1976 he campaigned for the reelection of United States Senator John Glenn Beall Jr.^[15]

He died of cancer at Walter Reed Army Medical Center at age 69.^[1]