On September 20, 1945, President Truman signs Executive Order 9621, dissolving the Office of Strategic Services effective October 1, 1945 — giving the agency just ten days to wind down. Intelligence functions are scattered: the Research and Analysis Branch transfers to the State Department (becoming the Bureau of Intelligence and Research), while clandestine intelligence and covert action elements move to the War Department's newly created Strategic Services Unit (SSU) under Brigadier General John Magruder. The OSS's 13,000 personnel are rapidly demobilized.
Truman had been fed disinformation about the OSS by J. Edgar Hoover. A February 19, 1945 article in the Washington Times-Herald — leaked by Hoover — published Donovan's secret November 18, 1944 memo to FDR proposing a permanent centralized civilian intelligence service, comparing it to a "Gestapo." The leak torpedoed public support, and after FDR's death Donovan's political position weakened further.
The dissolution creates the original intelligence revolving door. William "Wild Bill" Donovan — who built the OSS from his position as a Wall Street lawyer at Donovan, Leisure, Newton & Irvine — returns to his firm and immediately lobbies for a permanent civilian intelligence agency. Truman, wary of the Gestapo comparison, initially rejected the concept, creating the interim Central Intelligence Group in January 1946. But the institutional momentum Donovan and his allies created proves irresistible: by February 1947, Truman asks Congress to approve plans for a CIA "along the lines Donovan had proposed."
The OSS alumni network that disperses into the private sector in 1945-1947 will shape American intelligence for the next four decades. Allen Dulles returns to Sullivan & Cromwell (Wall Street's premier international law firm) before becoming CIA Director (1953-1961). William Casey moves between law, finance, and government before becoming CIA Director under Reagan (1981-1987). The pattern Donovan establishes — elite professionals moving from prestigious private-sector positions into intelligence, building the apparatus, returning to the private sector, then re-entering government at higher levels — becomes the permanent operating model of the intelligence community.
When the National Security Act of 1947 creates the CIA — signed by Truman on July 26, 1947, with the agency officially standing up on September 18 — the agency's culture, personnel networks, and institutional assumptions are shaped by OSS alumni who maintained their connections through Wall Street law firms, social clubs, and corporate boards during the two-year interregnum. A third of the CIA's initial personnel are OSS veterans. When Allen Dulles is assigned to draft the organizational proposal, he creates an advisory group of half a dozen men — all Wall Street investment bankers and lawyers. The CIA is not built from scratch — it is reassembled from a network that never fully dissolved, one that moved fluidly between government service and private-sector positions. This fluidity, initially a feature of elite patriotic service, becomes the structural foundation for the intelligence-industrial complex that emerges after the Cold War.