When was ended the OSS and created the CIA ?

Answer 1

After the US won in World War II, the OSS was disbanded by President Truman, on September 20, 1945. In the following month the functions of the OSS were split between the Departments of State and War. State received the Research and Analysis Branch of OSS which was renamed the Interim Research and Intelligence Service (IRIS) and headed by Alfred McCormack. The War Department took over the Secret Intelligence (SI) and Counter-espionage (X-2) Branches that were housed in a new office created for just this purpose - The Strategic Services Unit (SSU). The Secretary of War appointed Brigadier General John Magruder (formerly Donovan's Deputy Director for Intelligence in OSS) as director to oversee the liquidation, and more importantly the preservation of the OSS' clandestine intelligence capability.

Yet in January of 1946, President Truman created the Central Intelligence Group (CIG) which was the direct precursor to the CIA. The assets of the SSU, which now constituted a streamlined "nucleus" of clandestine intelligence was transferred to the CIG in mid-1946 and reconstituted as the Office of Special Operations (OSO). In 1947 the National Security Act established America's first permanent peacetime intelligence agency, the Central Intelligence Agency, which took up the functions of the OSS.