The OSS was formed as an agency of the Joint Chiefs of Staff (JCS)[3] to coordinate espionage activities behind enemy lines for all branches of the United States Armed Forces.

Donovan envisioned a single agency responsible for foreign intelligence and special operations involving commandos, disinformation, partisan and guerrilla activities.

[8] Writes Fink: Ellis was sent from New York by William Stephenson "to Washington to open a sub-station to facilitate daily liaison with Donovan, who reciprocated by sending [future Director of Central Intelligence, DCI] Allen Welsh Dulles to liaise with BSC in the Rockefeller Center".

The British immediately made available their short-wave broadcasting capabilities to Europe, Africa, and the Far East and provided equipment for agents until American production was established.

[10] Writes Fink: William Casey, who headed up OSS's Europe-based human-intelligence operations, the Secret Intelligence Branch, and went on to become director of the CIA, wrote in his autobiography, The Secret War Against Hitler, that Ellis was not only writing blueprints but involved in on-the-ground, logistical programs: "Dick Ellis, [an] experienced British pro, helped establish training centres, mostly around Washington."

Most famous were the operations in Switzerland run by Allen Dulles that provided extensive information on German strength, air defenses, submarine production, and the V-1 and V-2 weapons.

[12] For the duration of World War II, the Office of Strategic Services was conducting multiple activities and missions, including collecting intelligence by spying, performing acts of sabotage, waging propaganda war, organizing and coordinating anti-Nazi resistance groups in Europe, and providing military training for anti-Japanese guerrilla movements in Asia, among other things.

Among other activities, the OSS helped arm, train, and supply resistance movements in areas occupied by the Axis powers during World War II, including Mao Zedong's Red Army in China (known as the Dixie Mission) and the Viet Minh in French Indochina.

Some of these agents included exiled communists and Socialist party members, labor activists, anti-Nazi prisoners-of-war, and German and Jewish refugees.

The railroads connecting central Asia with Europe, as well as Turkey's close proximity to the Balkan states, placed it at a crossroads of intelligence gathering.

[21] Dogwood in turn hired a personal assistant named Walter Arndt and established himself as an employee of the Istanbul Western Electrik Kompani.

Schwarz was able to convince Romanian, Bulgarian, Hungarian, and Swiss diplomatic couriers to smuggle American intelligence information into these territories and establish contact with elements antagonistic to the Nazis and their collaborators.

[25] RYPE was the codename of the airborne unit who was dropped in the Norwegian mountains of Snåsa on March 24, 1945 to carry out sabotage actions behind enemy lines.

From the base at the Gjefsjøen mountain farm, the group conducted successful railroad sabotages, with the intention of preventing the withdrawal of German forces from northern Norway.

[29]: 101  Throughout the war years, the OSS Research & Development successfully adapted Allied weapons and espionage equipment, and produced its own line of novel spy tools and gadgets, including silenced pistols, lightweight sub-machine guns, "Beano" grenades that exploded upon impact, explosives disguised as lumps of coal ("Black Joe") or bags of Chinese flour ("Aunt Jemima"), acetone time delay fuses for limpet mines, compasses hidden in uniform buttons, playing cards that concealed maps, a 16mm Kodak camera in the shape of a matchbox, tasteless poison tablets ("K" and "L" pills), and cigarettes laced with tetrahydrocannabinol acetate (an extract of Indian hemp) to induce uncontrollable chattiness.

[29][30][31] The OSS also developed innovative communication equipment such as wiretap gadgets, electronic beacons for locating agents, and the "Joan-Eleanor" portable radio system that made it possible for operatives on the ground to establish secure contact with a plane that was preparing to land or drop cargo.

[33]: 5–7  While explaining the purpose and mission of his department and introducing various gadgets and tools, he reportedly casually dropped into a waste basket a Hedy, a panic-inducing explosive device in the shape of a firecracker, which shortly produced a loud shrieking sound followed by a deafening boom.

[46][47][48] Beginning in January 1941, Colonel Millard Preston Goodfellow, creator and Director of the Special Operations Branch (at this time still known as SA/G within the COI), negotiated with the National Park Service to obtain three tracts of land to be dedicated as training camps for both SA/G and SA/B.

[49] Commander N.G.A Woolley was loaned to COI by the British Navy and helped Donovan and Goodfellow to organize underwater training and craft landing.

[56] The main OSS training camps abroad were located initially in Great Britain, French Algeria, and Egypt; later as the Allies advanced, a school was established in southern Italy.

[56] The OSS's Mediterranean training center in Cairo, Egypt, known to many as the Spy School, was a lavish palace belonging to King Farouk's brother-in-law, called Ras el Kanayas.

Donovan sought independent thinkers, and in order to bring together those many intelligent, quick-witted individuals who could think out-of-the box, he chose them from all walks of life, backgrounds, without distinction to culture or religion.

In a matter of a few short months, he formed an organization which equalled and then rivalled Great Britain's Secret Intelligence Service and its Special Operations Executive.

Donovan, inspired by Britain's SOE, assembled an outstanding group of clinical psychologists to carry out evaluations of potential OSS candidates at a variety of sites, primary among these was Station S in Northern Virginia near where Dulles International Airport now stands.

[73] René Joyeuse M.D., MS, FACS was a Swiss, French and American soldier, physician and researcher, who distinguished himself as an agent of Allied intelligence in German-occupied France during World War II.

He received the US Army Distinguished Service Cross for his actions with the OSS, after the war he became a Physician, Researcher and was a co-founder of The American Trauma Society.

[74][75] "Jumping Joe" Savoldi (code name Sampson) was recruited by the OSS in 1942 because of his hand-to-hand combat and language skills as well as his deep knowledge of the Italian geography and Benito Mussolini's compound.

[80][81] Nisei linguists In late 1943, a representative from OSS visited the 442nd Infantry Regiment looking to recruit volunteers willing to undertake "extremely hazardous assignment.

SSU assets, which now constituted a streamlined "nucleus" of clandestine intelligence, were transferred to the CIG in mid-1946 and reconstituted as the Office of Special Operations (OSO).

[87] Today, the joint-branch United States Special Operations Command, founded in 1987, uses the same spearhead design on its insignia, as homage to its indirect lineage.