The Cold War
Introduction to the Cold War
The Second World War ended with Europe divided between the two superpowers, the United States and the Soviet Union.
Subversion and Soviet espionage were key concerns during the Cold War, and from the 1970s onwards terrorism also emerged as a serious threat to national security.
The story behind the 1947 controversy at a British interrogation centre in post-war Germany.
How MI5 worked to ensure the security of the late British Empire and the early Commonwealth.
How one of the Soviet Union's most valuable spies in the UK was exposed by MI5.
The arrest, trial and conviction of the Portland spy ring was one of MI5's most significant counter espionage successes.
Did the Security Service spy on Harold Wilson? The facts behind the long-running controversy.
Soviet, Eastern Bloc and Chinese espionage and the rise of terrorism in Northern Ireland during the Troubles.
Why MI5 was founded; the fight against German espionage; how MI5 caught German spy Carl Hans Lody.
The years immediately after the First World War saw MI5's size being reduced drastically as a result of post-war cost-cutting.
During World War II, the Security Service played a key role in combating enemy espionage, intercepting German communications and feeding misinformation back to Germany.
As the Cold War came to an end, terrorist threats from Northern Ireland and states such as Colonel Qadhafi's Libya became priorities for MI5.
You can learn more about the history of MI5 at The National Archives. We periodically release files to The National Archives which cover many aspects of our work.