Luther Green is an agent with E-1.
That organization is a ultra-secret department in the American intelligence community, one that has been around since the time of the O.S.S. but which has managed to remain largely unknown to the public and mostly unknown to those in the community. Initially it was known as Elite Corps (EC), established to find the best way to eliminate Hitler and many of his top officials. Some tries were successful, others not. After the war, as the OSS was being morphed into the nascent CIA, the EC was disbanded, or so it was officially stated.
Renamed E-1, the agency became an off-the-books organization, not existing but still quite busy and empowered to do in the shadows what the other Intelligence departments could not legally sanction. As put in a description, "if the government has secrets, then E-1 is the shadow of those secrets." At the time of the recorded adventures of Green, E-1 employed 50+ field operatives and a host of staff members to support each of their activities.
One of the very best of those operative is Luther Green. Skilled in several different martial arts, he is also deadly with a knife or a gun so when he is sent into the seamier, darker parts of a city to root out his enemies, he is more than capable of getting himself back out again. Being black lets him fit into many places where a white man would not only be quite noticeable, he would also be an irresistible target. Being highly intelligent and able to speak five languages, Green can also seem at home in more upscale locales but it seems that it is the dark alleyways that Green finds himself in more often.