Secrecy is one of the best currencies in war, so it's sometimes best for commanders to keep their best assets hidden from the enemy and the public. While the military has admitted that most of the units on this list existed at some point, a lot of their missions were classified for decades before being disclosed to the public. For the units that are still operating, America still only gets glimpses into their secret activities.
1. Task Force 88/Task Force Black
They may or may not be the same group and they may or may not still be in operation. Task Force Black and Task Force 88 are names floating around the media for the unit that conducted raids against terror organizations in Iraq and Afghanistan during the height of the wars. The unit was commonly described as being a joint U.S.-U.K. force made up of the best that SEAL Team 6, Delta Force, and the British SAS had to offer. Controversy erupted when they were blamed for a cross-border raid into Syria. There is speculation that Task Force Black may be back in operation to destroy ISIS, if it ever stopped.
2. 6493rd Test Squadron/6594th Test Group
These Air Force units existed from 1958 to 1986 and were tasked with catching "falling stars." They would fly out of Hawaii and catch film canisters falling from America's first spy satellites. The satellites, part of the Corona program, orbited the Earth and took photos of Soviet Russia. Then, the satellites would drop their film canisters over the Pacific ocean where these Airmen would try to snatch the canisters out of the air.
The recovery process was surprisingly low-tech. A plane with a large hook beneath its tail would try to catch the canister's parachute as it fell. When the planes failed to make the grab or the weather was too bad to attempt it, Coast Guard rescue swimmers in the unit would fish the film out of the water. The unit boasted a perfect record with more than 40,000 recoveries in 27 years. When its airmen weren't snatching film from the air, the unit supported rescue missions near Hawaii. It was credited with 60 saves.
3. Delta Force/Combat Applications Group/Army Compartmented Elements is more well known, but still pretty secret
Like many of the units on the list, Delta has gone through a few name changes over the years. Formation of an elite counter-terrorism unit had been proposed multiple times in the 1970s and Delta Force is widely believed to have been formed in late 1977. Its operational history got off to a horrible start with the failed Operation Eagle Claw in 1980. Since then, Delta has distinguished itself in combat from the invasion of Panama to the Gulf War to hunting Osama Bin Laden in the Tora Bora Mountains. Since the unit is still operational, many of their missions remain classified.
4. SEAL Team 6/DEVGRU
SEAL Team 6 specializes in counter terrorism, special reconnaissance, hostage rescue and close protection missions. You've probably heard of them, but many of their missions are still secret. Since 9/11, their budget and responsibilities have expanded to where they are now thought to have over 1,800 members, including some women who serve in intelligence roles. Perhaps most famous for both killing Osama Bin Laden and rescuing Captain Phillips from Somali pirates, it has been conducting combat operations since 1981.
5. 7781 Army Unit/39th Special Forces Operational Detachment
Operating in Berlin from 1956 to 1984, this team of green berets went through a few names during their history. They worked to keep West Berlin safe from communist incursions but also prepared to foment resistance if the city was taken over. Trained in classic spy craft skills, they were equipped with Bond-like gadgets such as cigarette-lighter guns and C-4 filled coal.
Master Sgt. Bob Charest, a retired former member of the unit, wrote for WATM about the unit.
6. The OSS
The Office of Strategic Services was formed in 1942 with the very broad mission of collecting and analyzing strategic information and conducting "special operations not assigned to other agencies." Since few agencies had special operators in World War II, this gave the OSS a lot of room to run. Under Col. William "Wild Bill" Donovan, the tiny agency conducted raids, smuggled weapons and spies, supported resistance groups in Axis territory, and collected intelligence. The OSS even employed the first "sea, air, and land" commando in U.S. history.