--- category: Intelligence & Government created: 2026-05-14 location: London, United Kingdom summary: MI6 (the Secret Intelligence Service, SIS) is the United Kingdom's foreign intelligence service, whose operations documented in this vault include the joint 1953 CIA-MI6 coup in Iran, Cold War coordination with the CIA on Afghanistan and elsewhere, the Robert Maxwell-Mossad intelligence network, and the Arms-to-Iraq affair. tags: - Organization - UnitedKingdom - Intelligence - MI6 - SIS - ColdWar updated: 2026-05-14 --- The Secret Intelligence Service (SIS), known popularly as MI6, is the [United Kingdom](/places/united-kingdom/)'s foreign intelligence service, responsible for collecting intelligence from overseas sources. It operates under the authority of the Foreign, Commonwealth and Development Office and reports to the Foreign Secretary, with parliamentary oversight through the Intelligence and Security Committee. Its legal basis was established by the Intelligence Services Act 1994. Its current headquarters, known as Vauxhall Cross, opened on the south bank of the Thames in [London](/places/london/) in 1994; the building's distinctive architecture made it a publicly known landmark, ending decades of official non-acknowledgment of SIS's existence.[^1] ### Origins and World War II SIS traces its origins to the Secret Service Bureau established in 1909, which split in 1910 into domestic (later [MI5](/organizations/mi5/)) and foreign intelligence (later SIS) sections. During [World War II](/events/world-war-ii/), SIS worked alongside the Special Operations Executive (SOE) and the American [Office of Strategic Services](/organizations/office-of-strategic-services/), forming the intelligence relationships - particularly with the United States - that became the post-war [Five Eyes](/organizations/five-eyes/) intelligence alliance. The [UKUSA Agreement](/programs/ukusa-agreement/) of 1946 formalized intelligence sharing between SIS's signals partner [GCHQ](/organizations/gchq/) and the American [National Security Agency](/organizations/nsa/).[^1] ### Operation Boot: The Iran Coup SIS's most historically significant joint operation with the [Central Intelligence Agency](/organizations/central-intelligence-agency/) was Operation Boot (the American component was called Operation Ajax) in August 1953. British and American intelligence officers, including SIS officer Norman Darbyshire and CIA officer Kermit Roosevelt Jr., organized a coup in [Iran](/places/iran/) that removed elected Prime Minister Mohammad Mosaddegh and restored [Shah Mohammad Reza Pahlavi](/people/mohammad-reza-pahlavi/) to full power. The British motivation was primarily the recovery of nationalized Anglo-Iranian Oil Company assets; the American motivation was preventing a communist takeover. The operation established the template for Cold War covert regime change and the long-term relationship between the CIA and [SAVAK](/organizations/savak/), the Shah's intelligence service.[^2] ### Cold War Operations SIS maintained liaison relationships with intelligence services across the Middle East, Africa, and Asia throughout the Cold War. Its cooperation with Mossad - the [Israeli](/places/israel/) intelligence service - is described in numerous memoirs and investigative accounts as extensive, covering operations in Arab states, Iranian intelligence assessments, and personnel exchanges. [David Kimche](/people/david-kimche/), the senior Mossad officer who initiated the Iran-Contra arms channel, was born in [London](/places/london/) and cultivated SIS relationships throughout his career. In [Afghanistan](/places/afghanistan/), SIS coordinated with the CIA's Operation Cyclone through SAS training programs for mujahideen fighters during the Soviet occupation (1979-1989). The relationship between SIS and Pakistan's ISI during this period was close and operationally significant.[^1] ### Robert Maxwell Multiple former intelligence officers, including [Ari Ben-Menashe](/people/ari-ben-menashe/) and Victor Ostrovsky, asserted that press baron [Robert Maxwell](/people/robert-maxwell/) worked simultaneously for [Mossad](/organizations/mossad/) and had relationships with multiple Western intelligence services including SIS. Maxwell's access to senior British politicians, his publishing empire (which included scientific journals widely distributed in the Soviet bloc), and his Central European connections made him valuable to intelligence services. [Nicholas Davies](/people/nicholas-davies/), his Daily Mirror foreign editor, was accused of operating as a Mossad asset. SIS's relationship with Maxwell was not officially confirmed.[^2] [^1]: "Secret Intelligence Service (SIS/MI6)," UK Government. https://www.gov.uk/government/organisations/secret-intelligence-service [^2]: Dorril, Stephen. *MI6: Inside the Covert World of Her Majesty's Secret Intelligence Service.* Free Press, 2000.