Special Liaison Units

Special Liaison Units (SLU) were part of the British Secret Intelligence Service (see MI6), formed in 1940 to convey ULTRA intelligence to British, and later US, Cs-in-C in the field. SLUs, which worked in the utmost secrecy, were attached to the HQ of those commanders cleared to receive ULTRA. They comprised two sections: the Special Communications Unit (SCU), manned by army personnel, and the Special Liaison Unit, mostly manned by RAF personnel. The former received the ULTRA intelligence—transmitted from the British Code and Cypher School at Bletchley Park by the one-time pad method of encodement or later by the Typex machine—and the latter deciphered and disseminated it. After it had been digested by the army commander, or by one or his staff officers who had been cleared to receive it, the SLU officer ensured it was destroyed.

Prior to the Normandy landings in June 1944 (see OVERLORD) the Americans began using an ‘ULTRA representative’ who received the deciphered signals from the SLU, digested the information in them, and then presented it at regular briefings to the commander in the field or his senior staff officers. The ULTRA representative was also empowered to combine it with intelligence from other sources and to give operational advice on its use in such a way as to protect its origin. They were trained at Bletchley Park and numbered only 28 in all.

Bibliography

Lewin, R. , ULTRA Goes To War (London, 1978).