The United States Central Intelligence Agency (CIA) dates from September 18, 1947, when President Harry S. Truman signed the National Security Act of 1947 into law. A major impetus that has been cited over the years for the creation of the CIA was the unforeseen attack on Pearl Harbor, but whatever Pearl Harbor's role, at the close of World War II government circles identified a need for a group to coordinate government intelligence efforts, and the Federal Bureau of Investigation (FBI), the State Department, the War Department, and even the Post Office were all jockeying for that new power.
General William "Wild Bill" Donovan, head of the Office of Strategic Services (OSS), wrote to President Franklin D. Roosevelt on November 18, 1944, stating the need for a peacetime "Central Intelligence Service ... which will procure intelligence both by overt and covert methods and will at the same time provide intelligence guidance, determine national intelligence objectives, and correlate the intelligence material collected by all government agencies", and have authority to conduct "subversive operations abroad", but "no police or law enforcement functions, either at home or abroad". Donovan's letter was prompted by a query from General Dwight Eisenhower's Chief of Staff about the nature of the role of the OSS in the military establishment. Following this, Roosevelt ordered his chief military aide to conduct a secret investigation of the OSS's World War II operations. Around this time, stories about the OSS began circulating in major papers, including references to this OSS follow-on being an "American Gestapo". The report, heavily influenced by an FBI that saw itself as the future of American foreign intelligence, was starkly and vividly negative, only praising a few rescues of downed airmen, sabotage operations, and its deskbound research- and analysis-staff; the pronouncement of the report was that any "use [of the OSS] as a secret intelligence agency in the postwar world [would be] inconceivable", but even before the report was finished the President - presumably under pressure from the press articles - had ordered the Joint Chiefs to shelve their plans for a Central Intelligence Service even before the April release of the report.
On September 20, 1945, as part of Truman's dismantling of the World War II war machine, the OSS, at one time numbering almost 13,000 staff, was eliminated over the span of ten days. A reprieve, though, was granted six days later by the Assistant Secretary of War, reducing it to a skeleton crew of roughly 15% of its peak force level, forcing it to close many of its foreign offices; at the same time the name of the service was changed from the OSS to the Strategic Services Unit.
Immediate predecessors, 1946–47
During World War II, President Roosevelt was concerned about American covert intelligence capabilities, particularly in the light of the success of Churchill's Commandos. On the suggestion of a senior British intelligence officer, he asked Colonel William "Wild Bill" Donovan to devise a combined intelligence service modeled on the British Secret Intelligence Service (MI6), and Special Operations Executive, centralizing, for instance, the separate cryptanalysis programs of the Army, and Navy. This resulted in the creation of the Office of Strategic Services. On September 20, 1945, shortly after the end of World War II, President Harry S. Truman signed Executive Order 9621, dissolving the OSS by October 1, 1945. The rapid reorganizations that followed reflected not only routine bureaucratic competition for resources but also exploration of the proper relationships between clandestine intelligence collection and covert action (i.e., paramilitary and psychological operations). In October 1945, the functions of the OSS were split between the Departments of State and War: