The incredible true story of the first four Nazi spies to infiltrate British soil is revealed in this WWII history. After the swift takeover of France and the Low Countries, Nazi Germany was on the crest of a wave. Only the United Kingdom stood in its way. Hitler quickly devised plans for the invasion of England, codenamed Operation Sealion. To lay the groundwork, a team of spies would be sent in advance to act as pathfinders for the incoming forces. Codenamed Operation Lena, this phase of the plan was considered a suicide mission by German military intelligence. They had only thirty days to recruit and train agents who had a less than convincing grasp of English language or customs. Hitler's Spies revels the story of the first four agents to arrive on English soil—collectively known by MI5 as "The Brussels Four." Using a wealth of primary materials, including newly declassified sources, Mel Kavanagh sheds light on one of the most audacious yet little-known operations of the Second World War, in which undertrained men were sent behind enemy lines at a time when Britain was gripped by spy paranoia.