This thesis examines, by reference to the political,institutional, organisational, personnel, operational, methodologicaland technical aspects of naval intelligence work, the developmentalaspects of its history from 1880 to 1945. By analysing specific navaloperations and discussing the strategic and tactical ramifications ofintelligence it seeks to throw light on the impact of intelligence onnaval warfare in this period. In so doing it reveals the place ofintelligence in the general naval history of the period. It is not adefinitive history, but rather a discursive analysis of those aspectsconsidered the most important.In the pre-1914 era the N.I.D. was the heart of theemergent Naval Staff, involved in strategic planning at the highestlevel. World War I brought the need for an operational intelligenceorganisation, with the priority of locating, identifying, and deducingthe intentions of major German units. Experience in war revealedthe necessity for a clear definition of the relationship between theOperations Division and the N.I.D. The use of radio intelligenceand cryptanalysis gave N.I.D. great operational successes andAdmiral Hall the opportunity to involve N.I.D. in political issues.The latter led to the review of N.I.D.'s role post 1918 and, in part,its run-down. The inter-war period witnessed N.I.D.'s declineas the most dynamic and influential Naval Staff department. Untilthe foundation of O.I.C. and the coming of war N.I.D. was a backwater.World War It witnessed a re-vitalisation, a more structuredand tightly controlled N.I.D., and the D.N.I.. as an importantechelon of the C.O.S. and J.LC. organisations. N.I.D. regainedits previous supremacy and was instrumental in the process towardsintelligence integration at the end of World War U. It scored greatoperational successes.The function of intelligence is demonstrated as beingparamount in the naval organisation and critical to the interestsof the State. Its maintenance was contingent upon variables which,throughout this period, were neither constant nor always recognised.