German espionage in Great Britain during the First World War era provides a continuing source of fascination, but the true activities of the 'Spies of the Kaiser' have long been shrouded in mystery. Thomas Boghardt's study, based on hitherto untapped British and German sources, examines for the first time the scope and objectives of German covert operations in Great Britain before and during the First World War, and challenges the traditional view that MI5, the British security service, was able to thwart German espionage. Spies of the Kaiser reveals how the German secret services employed anthrax and sabotage against the Allies in the First World War and how the spectre of German espionage profoundly shaped the emerging British intelligence community. It is a highly relevant and timely book for today's world in which terrorist threats and the role of the secret services in democratic societies remain intensely debated issues.