MI5 at War 1909-1918

The years 1909-1918 can be regarded as formative for MI5, an era in which it developed from a small counterespionage bureau into an established security intelligence agency. MI5 had two main roles during this period; counterespionage, and advising the War Office on how to deal with the police and the civilian population, particularly foreign nationals in Britain. Using hitherto neglected documents from official archives, this study examines how MI5 foiled the spies of the Kaiser during the First