MI5

MI5, British security service which in the Second World War, as in the First, shared with MI6 and the Special Branch of the Metropolitan Police the responsibility of evaluating, and advising the British government on, intelligence relating to national security, this being defined as ‘the defence of national interests against hostile elements other than the armed forces of the enemy: in practice against espionage, sabotage and attempts to procure defeat by political subversion’.

The dividing line between MI5 and MI6, which went back to the establishment of the two bodies under the war office before the First World War, was geographical. MI5's responsibility extended to the three-mile limit off the UK and, in co-operation with the local authorities, of the countries of the empire, including Egypt (see Security Intelligence Middle East), while MI6 (the body primarily concerned with collecting intelligence abroad, which was officially named the Secret Service or the Secret Intelligence Service from 1921) was also responsible for national security beyond those limits.

Within the UK MI5 reverted after the First World War to being a small section of the war office charged only with security on behalf of the armed forces, and the Special Branch was made responsible for security as it affected the civilian population. This change was made in response to ministerial, public, and police distrust of the development of a domestic secret service at a time when the increasing prominence of labour organizations, pacifist groups, and communist activists was blurring the distinction between subversion and legitimate disaffection—and when espionage had ceased to be an obvious threat. But the resultant duplication and friction were such that in 1931 MI5 (now officially named the Security Service but also, like MI6, retaining its old title for reasons of custom and convenience) took over the responsibility for evaluating and advising on all intelligence relating to subversion (other than that relating to known Irish and anarchist groups and to the maintenance of public order, which remained in the province of the Special Branch) and to espionage. The responsibility for taking executive action on the intelligence remained with the Special Branch and the chief constables under the authority of the home secretary. As the Security Service, MI5 was also made accountable to the home secretary in view of his constitutional responsibility both for the safety of the state and for the liberty of the subject and the rights of minorities.

With the outbreak of hostilities in September 1939 MI5 perforce delegated its direct responsibility abroad, in Egypt and at British bases, to the military authorities. Otherwise the above arrangements remained unchanged throughout the war. Clashes of jurisdiction with MI6 in the field of counter-espionage revived suggestions that MI5 should either be incorporated into MI6 or should assume responsibility for all counter-espionage, both at home and abroad. But practical experience and constitutional considerations—MI6 was accountable to the foreign office—dictated the retention of a separate security service for British territory.

Disagreements relating to security against the threat of subversion in the UK were less frequent, and they were not clashes about jurisdiction between MI5 and the police but differences of judgement between MI5, supported by the police, and the home office. The earliest of them, and the most prolonged, persisted throughout the first year of the war. The home office, with its concern for the liberty of the individual, was slower to implement against enemy aliens, and the potentially dangerous British fascist and communist organizations, some of the formidable array of emergency Defence Regulations drawn up before the war (under the royal prerogative or by extension of the Official Secrets Acts and the Aliens Restrictions Acts) than MI5, with its responsibility for security, thought advisable; and after the fears let loose by the German offensives in the west in May 1940 (see FALL GELB) had prompted the hasty application of drastic measures during the fifth column panic of July 1940 (see internment), the home office was quicker to relax them than MI5 desired. A similar conflict arose in the last eighteen months of the war: MI5 then pressed to little avail for the exclusion from government service of communists, who had been excluded from the application of the security measures adopted in 1940.

As before, it drew a distinction between known members of the Communist Party, or people known to have close associations with them, and people who, though known to have once had some association, had long since ceased to give grounds for concern. It had no evidence during the war that a few in the latter category who were active on behalf of the Soviet authorities after entering government service included employees of MI6 and MI5 itself (seespies).

MI5 naturally kept a watch on known adherents of Mosley's fascist organization (see British Union), and on those who had advocated close Anglo-German friendship before the war began. Among this latter group, one of MI5's undercover women agents found a White Russian refugee woman who had befriended a cipher clerk in the US embassy in London, called Tyler Kent. Kent was strongly opposed to Roosevelt's policy of friendship with the UK, and stole from the embassy texts of telegrams exchanged between Roosevelt and Churchill, which he hoped to be able to release to the public in some way that would ruin Roosevelt's chances of re-election to the presidency in November 1940. Joseph Kennedy (1888–1969), the US ambassador, was persuaded to waive Kent's diplomatic immunity; Special Branch raided Kent's flat, and found the telegrams. The young man was tried in camera and sent to prison.

In the arguments preceeding the fifth column panic MI5 had been doubly handicapped. Its staff—some 400 in total, as compared with 800 in 1918—was overwhelmed and its headquarters disorganized by an enormous increase in such mundane if necessary work as the vetting of entrants into government service, the organization of travel controls, and the scrutiny of floods of neurotic reports from the public denouncing aliens and suspected enemy agents. In the second place, it was in the unenviable position of having to assume in the absence of reliable negative evidence that an organized subversive movement, harbouring enemy agents, might be reporting abroad and even waiting for the opportunity to strike. The first handicap largely disappeared in the wholesale tightening up of security procedures effected during the panic by a new security executive set up under an ex-cabinet minister, Lord Swinton: under his supervision its sections were reorganized and its more humdrum duties were decentralized to the chief constables.

At the same time Churchill noticed that MI5 was still headed by Sir Vernon Kell, who had founded it in 1909 and was in the new prime minister's opinion no longer fit for the task. Kell was abruptly retired. For a few months the organization was run by Brigadier ‘Jasper’ Harker, one of his subordinates, while his successor returned from abroad. This was Sir David Petrie, who had had 36 years' continuous service in the Indian police and thus had every aspect of security at his fingertips. He worked easily with the many newcomers into his department, most of them university dons.

The removal of the second handicap—the dearth of reliable intelligence—did not follow from these steps. It was brought about by developments which coincided with the reorganization, when the morale and the reputation of MI5 were at their lowest ebb. MI5 had fretted over the lack of evidence for an organized fifth column when no such thing existed; but it could not confirm the non-existence before suspects had been interned and could be interrogated. In the same way, the fact that it had detected some 30 cases of attempted espionage before the outbreak of war had only persuaded it that others might have escaped detection and that from the beginning of the war their numbers were increasing (which was not the case). Whatever its faults, complacency was not among them. It was correspondingly quick to exploit opportunities thrown up by the outbreak of hostilities. It used the fact that an Abwehr agent volunteered his services in September 1939, and a second in January 1940, to introduce to the Abwehr two further double agents by August 1940. It took full advantage of the fact that from August 1940 the first radio transmissions associated with the Abwehr's plans against the UK were intercepted by the Radio Security Service (RSS) and decrypted by the government Code and Cypher School at Bletchley Park. With the aid of these two sources, double agents and signals intelligence, it directed the total defeat of the first Abwehr offensive against the UK from September to November 1940, when all but one of the 21 agents who arrived were either immediately captured or immediately gave themselves up; the exception committed suicide.

From this success, as from its equal success in intercepting the agents the Abwehr continued to try to infiltrate into the UK at the rate of some 20 agents a year till the end of 1943, MI5 acquired more double agents. Others were Abwehr employees who from January 1941 volunteered their services; they included the few who, under the codenames TRICYCLE ( Popov), GARBO ( Pujol), and BRUTUS ( Garby-Czerniawski), came to be the most valuable. A similar expansion took place in the signals intelligence provided for MI5 from December 1940, when Bletchley Park cryptographers began to read the main hand ciphers of the Abwehr, and even more so from December 1941, when they mastered the Abwehr's version of the ENIGMA machine cipher. By then MI5 and MI6 had built up so full a knowledge of the order of battle and operations of the Abwehr throughout Europe (as also, to a lesser extent, in the Middle East and Latin America) that, though remaining a considerable nuisance in areas where effective action against it was difficult to mount (particularly Spain and Gibraltar), the Abwehr presented no threat within the UK for the rest of the war. Indeed, its activities were turned into a substantial liability for Germany by the decision to use the double agents for deception.

The prime purpose to which MI5 put the intelligence was to advance security by persuading Germany that it was so well served by agents that it need not struggle to develop new methods for infiltrating others. Not until it could be confident that it controlled all agents in the country, and would not fail to detect new arrivals, could MI5 pay serious attention to using the double agents to pass misleading information as part of a sustained programme of strategic deception about the resources and the intentions of the Allies. That point was reached in the middle of 1942. Thereafter, though only as one element in a complex machine directing strategic deception in support of Allied operations from the UK, the London Controlling Section (see UK, 8), and the XX-committee, MI5 made a crucial contribution to the deception plans by choosing and briefing the double agents. In the Middle East and the Mediterranean parallel machinery for the control of deception was set up under the military authorities, and MI5 played only an advisory role.

Whatever benefit the Allied operations derived from the deception programme, it must be stressed that suggestio falsi was of less consequence than suppressio veri. Deception could be instrumental in the success of the operations, notably of the Normandy landings in June 1944 (see OVERLORD), only if the Allies were able to conceal their true intentions. They owed their success in achieving this to the general weakness of Germany's intelligence sources, the check on enemy espionage, in which MI5 played the leading role, and their own meticulous security precautions, which were drawn up and supervised by yet another complex machine, a strengthened Inter-Services Security Board, with advice from MI5.

F. H. Hinsley

Bibliography

Andrew, C. , Secret Service: The Making of the British Intelligence Community (London, 1985).
Curry, J. C. , The Security Service 1908–1945 (London, 1999).
Hinsley, F. H., and and Simkins, C. A. G. , British Intelligence in the Second World War, Vol. 4: Security and Counter-Intelligence (London, 1990).