The Ph.D. thesis chronicles the establishment and history of the Defense Intelligence Agency under its first director, Lt. General Joseph Carroll, from 1961-1969. Based on published works, archival materials, declassified documents, and interviews with cognoscenti, the thesis explores the creation of the agency in the context of the historical propensity to consolidate common military functions under the auspices of the Office of the Secretary of Defense. Although the intelligence function of the military departments resisted this trend for over two decades after the Second World War, by 1960 the perceived failures of military espionage made the consolidation of this function ineluctable. Impelled by the recommendations of the Joint Study Group, in 1961 Secretary of Defense Robert McNamara concluded that the creation of a potent military intelligence agency was necessary to meliorate the strategic estimate process - which he believed to be flawed and ineffectual - through the centralisation of military espionage activities. The military leadership was averse to this design, alternately favouring the establishment of a weak co-ordinating body as a means to preserve the autonomy of existing military structures. After fervent debate, the DIA was eventually created as a compromise between both factions. The thesis argues that the history of the agency, its successes and failures, largely has been the result of the dialectic between both visions of the agency. Caught between the dissimilar, often competing, requirements and expectations of its two masters - the Office of the Secretary of Defense and the Joint Staff - the agency strove to forge its identity, establish and preserve its autonomy, and secure the resources necessary to fulfil its responsibilities.