The Office of Strategic Services (OSS) was formed during WWII in 1942, was dissolved in 1945, and is the precursor to the Central Intelligence Agency (CIA), formed in 1947.
During the war, it was essential for espionage, propaganda, subversion, and post-war planning.
Wikipedia, while not being "the last word" on this important department, certainly has enough to get you going. One day, I hope to have a conversation about the Office on this thread, but we'll need to get some interested parties first.
This tape will self-destruct in five seconds. Good luck, Jim.