This is a documentary history of how intelligence influenced Britain's policy response to key 20th century events. For more than 50 years, the Joint Intelligence Committee (JIC) has been central to the secret machinery of the British Government, acting as a broker between the realms of the spy and the policy-maker. From WWII to the War in Iraq, and from the Falklands to the IRA, it has been involved in almost every key foreign policy decision. These 18 case studies look at key moments in the JIC's history. Each case study includes a contextualising introduction, a full reproduction of an original JIC document that influenced the government's policy response to a particular situation and explanatory footnotes. It features 18 case studies that pinpoint the role of intelligence in foreign and defence policy from 1936 to the present day. It reproduces the original versions of declassified intelligence assessments and reports. It is suitable for students and academics studying contemporary international history and government policymaking processes.