Established on July 11, 1941, the Office of the Coordinator of Information (COI) was to be the United States of America
's first serious and organized venture into espionage, propaganda, subversion, and the various other activities, all under one agency. These functions had all been performed before by the United States, but never by one cohesive centralized organziation. The COI had a 10 million dollar starting budget, and an initial workforce of some 600 people, both military and civilian (Eventually, the OSS would grow to nearly 20,000 men and women).
The creation of the COE spawned from two special missions that William Joseph Donovan performed for the President of the United States, Franklin D. Roosevelt. Roosevelt saw the value of having missions of this secret nature conducted regularly by an actual organization, so he asked Donovan to help form an American intelligence agency.
The United States Army and the Navy both objected strenuously to this new agency. They feared that it would take away from many of the intelligence roles that the two military branches traditionally performed. In order to help appease these objectors, it was decided that the COI would report directly to the President and the Joint Chiefs of Staff. It was definitely stated that many intelligence functions would always be reserved duties of the Navy and Army.
In June of 1942, the COI was renamed the Office of Strategic Services (OSS). Some of the duties that came with the name change included foreign counterintelligence activities, under the section known as X-2. Intially, the OSS was not privy to the highly secret ULTRA, MAGIC, and ICE, but eventually X-2 did receive the necessary clearance.
During 1942, Donovan sent intelligence units to every theatre of war that would accept them. Some battle areas, such as French North Africa desperately needed intelligence, so they were welcomed. However, both General Douglas MaArthur and Admiral Chester Nimitz essentially shut the OSS out of the Pacific Theatre of Operations against the Empire of Japan.
Some of the operations the Office of Strategic Services was involved in:Aided guerilla/partisan operations in Europe, Asia
'Black' propaganda (made to look like it was coming from disgruntled Germans or Japanese)
Ran bureaus in neutral Switzerland so anti-Hitler Nazis could send status reports
Adopted remnants of prewar French intelligence units, who provided much valuable intel on German army deployments in France
Helped smuggle Danish physicist Niels Bohr out of German-controlled Europe
Sent an agent to assassinate German physicist Werner Heisenberg (did not go through, though)
The OSS conducted many operations during World War II, with units of many different military disciplines. There were US Army Air Corps bomber crews, Navy divers, civillians working with anti-Japanese guerillas in East Asia, etc.
After World War II, in 1945, the OSS was dissolved. It's remnants were dispersed among the various military branches, and eventually some of the other sections were transformed into the Central Intelligence Agency