A recently declassified document obtained by The Black Vault Freedom of Information Act archive, shows that hypnosis was investigated for military applications. However, the overall conclusion of the study was that there was no evidence that hypnosis could be used for military applications, and also that there was no clear evidence for whether 'hypnosis' actually exists as a definable phenomena outside of ordinary suggestion, high motivation and subject expectancy. According to the document,
The use of hypnosis in intelligence would present certain technical problems not encountered in the clinic or laboratory. To obtain compliance from a resistant source, for example, it would be necessary to hypnotise the source under essentially hostile circumstances. There is no good evidence, clinical or experimental, that this can be done.
Furthermore, the document states that:
It would be difficult to find an area of scientific interest more beset by divided professional opinion and contradictory experimental evidence…No one can say whether hypnosis is a qualitatively unique state with some physiological and conditioned response components or only a form of suggestion induced by high motivation and a positive relationship between hypnotist and subject…T.X. Barber has produced “hypnotic deafness” and “hypnotic blindness,” analgesia and other responses seen in hypnosis—all without hypnotizing anyone…Orne has shown that unhypnotized persons can be motivated to equal and surpass the supposed superhuman physical feats seen in hypnosis.
The study concludes:
It is probably significant that in the long history of hypnosis, where the potential application to intelligence has always been known, there are no reliable accounts of its effective use by an intelligence service.
Research into hypnosis in military applications is further verified by the MKULTRA experiments, also conducted by the CIA. According to Congressional testimony, the CIA experimented with utilizing LSD and hypnosis for mind control. Many of these programs were done domestically and on participants who were not informed of the study's purposes or that they would be given drugs.
The full paper explores the potentials of operational uses.