Why Is It Called Mi5 and Mi6?

"MI5/MI6" were the original designations when both organisations came under the War Office, now the MOD - "MI" stands for military intelligence. Their official names (acquired in the 30s) are the Security Service (MI5) and SIS, the Secret Intelligence Service (MI6).

What is the difference between MI5 and MI6 and MI7?

MI5: Liaison with Security Service, following the transfer of Security Service to the Home Office in the 1920s. MI6: Liaison with Secret Intelligence Service and Foreign Office. MI7: Press and propaganda (transferred to Ministry of Information in May 1940). MI8: Signals interception and communications security.

What does MI7 stand for?

During the first world war British Intelligence created the Military Intelligence Section 7 (or MI7 for short) that was responsible for collecting data from foreign sources, translating it, and transmitting it back to the allied leadership.