Because of the politically sensitive and often quite unsavory aspects of their work, but also because they wish to protect their former agents, secret services usually do not like to say very much about their past activities and try to keep their records out of the hands of historians and other outsiders for as long as possible. The army intelligence service of Imperial Germany—officially known as the Geheime Nachrichtendienst des Heeres or, more simply, as the “N.D.”—was no exception to this rule. While the last chief of that organization, Walter Nicolai, and some of his former subordinates wrote a number of books and articles after 1918 in which they described the functions of the N.D. and some of its accomplishments, they remained studiously vague on many issues, particularly with regard to the espionage operations which had been conducted in the Entente countries in the years prior to the Great War. As might be expected, various other German publications on the background of the war which appeared in the 1920s and 1930s, including Die Grosse Politik der Europäischen Kabinette and other such editions of government documents, similarly maintained a discreet silence on this subject.