Captain Sir Mansfield George Smith-Cumming KCMG CB (1 April 1859[3] – 14 June 1923) was a British naval officer who served as the first chief of the Secret Intelligence Service (SIS).

[8] In 1909, Major (later Colonel Sir) Vernon Kell became director of the new Secret Service Bureau and created as a response to growing public opinion that all Germans living in England were spies.

[10] Budgets were severely limited prior to World War I, and Cumming came to rely heavily on Sidney Reilly (aka the Ace of Spies), a secret agent of dubious veracity based in Saint Petersburg.

[11] At the outbreak of war he was able to work with Vernon Kell and Sir Basil Thomson of the Special Branch to arrest twenty-two German spies in England.

Agents who worked for MI6 during the war included Augustus Agar, Paul Dukes, John Buchan, Compton Mackenzie and W. Somerset Maugham.

Cumming also began importing some of his own veteran case officers into Ireland from Egypt, Palestine, and India, while Basil Thomson organized a special unit consisting of 60 Irish street agents managed by communications from Scotland Yard in London.

[15] On Sunday, 21 November 1920, the Headquarters Intelligence Staff of the IRA and its special Counterintelligence Branch under the leadership of Michael Collins assassinated 14 of Cumming's case officers.