German Spies at Bay: Being an Actual Record of the German Espionage in Great Britain during the years 1914-1918, compiled from Official Sources

This book brings together accounts of German spies operating in Great Britain during World War I, along with the methods British counter-espionage agents used to track them down. The German Secret Service began building a network of agents in Britain as early as 1905, mainly to gather information about naval operations. By the time war broke out in the summer of 1914, British authorities were already aware of many of these spies and quickly moved to keep them under watch. Britain’s willingness to devote more resources to counterintelligence than Germany put into spying, along with a patient approach to observing enemy activity, played a major role in its success in largely shutting down German espionage efforts. (Summary by Ted Lienhart)