In late-1943, some officers in the Abwehr, Germany's military intelligence service during the Second World War, began planning for a withdrawal of troops from occupied Western Europe. ‘Operation Easter Egg’ was initiated. Caches of explosives and sabotage material were buried and location maps drawn. Nazi collaborators were recruited to be trained at special schools as saboteurs, espionage agents and wireless operators. The plan was to have them stay behind once the Germans retreated, locate the caches and undertake sabotage on Allied lines of communication. There were stay-behind groups in Italy. Some were members of the Decima Flotilla MAS, also known as X MAS, a naval assault group which had launched numerous attacks on Allied shipping between 1940 and 1943. After the Italian Armistice in September 1943, Prince Valerio Borghese, the X MAS Commander called by some 'The Black Prince', collaborated with the Germans and in 1944 began to set up stay-behind groups in Turin, Genoa, Bologna, Milan and Venice. In April 1945, Mario Rossi, the leader of these stay-behind groups, was captured by the Allies and interrogated. Over the following months, members of the X MAS stay-behind groups were arrested and interrogated. Their interrogation reports, deposited after the war in the National Archives in Kew, shed light on the organisation, its administrators, its training schools, the students, the syllabus, their equipment and in some cases their missions. Bernard O’Connor’s documentary history provides first-hand evidence of the X MAS stay-behind organisation and the day-to-day dealings of British and American counter-intelligence officers whose job it was to identify threats to the security of Allied forces in Italy, apprehend those responsible, locate and confiscate their equipment, interrogate the agents and learn as much as they could about the enemy’s plans and their organisation.