Before Delta Force existed, there was the OSS.
And while the World War II Office of Strategic Services (OSS) was technically a military agency under the Joint Chiefs of Staff, in practice it was fairly autonomous of military control and enjoyed direct access to President Franklin D. Roosevelt.
Major General William Joseph Donovan was the head of the OSS. Donovan was a soldier and Medal of Honor recipient from World War One. He was also a lawyer and former classmate of FDR at Columbia Law School. Like the subsequent CIA, OSS included both human intelligence functions and special operations paramilitary functions.
Its Secret Intelligence division was responsible for espionage, while its Jedburgh teams, a joint U.S.-UK-French unit, were an ancestor of groups that create guerrilla units, such as the U.S. Army Special Forces and the CIA. OSS' Operational Groups were larger U.S. units that carried out direct action behind enemy lines. Even during World War II, the idea of intelligence and special operations units not under strict military control was controversial.
OSS operated primarily in the European Theater of Operations (ETO) and to some extent in the China-Burma-India Theater, while General of the Army Douglas MacArthur was extremely reluctant to have any OSS personnel within his area of operations.