Since before the U.S. was even a country, elite and secret units have played important roles in military actions. The first recorded Ranger unit in the Americas took part in King Phillip’s War in 1670. A century later, Maj. Robert Rogers’s Rangers would follow his 28 Rules of Ranging in their fight with the French.

And then there are the Marines who, along with a group of mercenaries, captured Derna, Tripoli in 1805. First Lt. Presley O’Bannon led the eight U.S. Marines who fought in the battle, deposing Tripolitanian Bashaw Yusuf Karamanli. The men marched for six weeks to cover the desert from Egypt to Tripoli, and faced a force of over 2,000 when they arrived there. The fall of the city led to the surrender of Bashaw Yusuf. The Marines’ exploits are even immortalized in the Marines’ Hymn.

A Long History of Secret Units Fighting in America’s Wars

The history of the U.S. special operation units has its most commonly identifiable starting point in WWII. Every branch got in on the action, from the Navy’s frogmen to Doolittle’s Raiders. Yet, the history of secret U.S. military units does not begin there.

During the Civil War, Union soldiers known as “Jessie Scouts” donned Confederate uniforms and rode into enemy territory to gather intelligence. Working under Gen. Philip Sheridan, the Jessie Scouts even appear to have been involved in missions across the Mexican border following the end of the war.

The heritage of the earliest elite and secret units lives on to this day in the insignia of America’s warfighters. Even the crossed arrow patch worn by U.S. Army Special Forces tracks a lineage to the Native Americans who enlisted to serve as Army Scouts following the Civil War.

A World at War and the Flourishing of Special Units

Doolittle raid
Lt. Col. James “Jimmy” Doolittle performs a full-throttle takeoff from the USS Hornet 650 miles from Japan. (U.S. Air Force)

The U.S. fought in WWI, but coming out of an isolationist footing, it wasn’t as involved in that first great war as it was in WWII. 

For the U.S. Navy, the move into special operations grew out of the need for intelligence on landing beaches. Phil H. Bucklew, credited as the “Father of Naval Special Warfare,” was with the first Amphibious Scouts and Raiders group formed in 1942. These brave men, who would not only reconnoiter landing sites, but hold them and guide in the assault waves, are considered to be the forebears of Navy SEALs.

Lt. Col. James H. Doolittle and his Doolittle’s Raiders from the 17th Bombardment Group, U.S. Army Air Forces, blazed the trail for airmen in special operations. Their famed raids, which reached Tokyo, had been preceded by extensive specialized training in night flying and other skills. When they launched from the USS Hornet on April 14, 1942, the 16 B-25s were on a one-way trip. The crews knew they would not be able to return to the American carrier. Fifteen of the crews crashed in Japanese-occupied China, and one landed in the Soviet Union, where they were interned. 

The Marines got a bit of a jump on their special operations, with the 1st Reconnaissance Battalion which was activated in 1937 and began deployments to the Caribbean in 1940. They were followed by the 1st Raider Battalion, activated in February of 1942 under Lt. Col. Merritt Edison. Those early Raider battalions were disbanded near the end of the war.

The Marine Corps Scout Snipers had their start in the Pacific. Under the tutelage of Lt. Col. William “Wild Bill” Whaling, the 1st Marine Division began training select individuals on scouting and spearheading operations in Guadalcanal.

From Rangers to Scouts, the U.S. Army had a number of specialized units serving in WWII, including the Alamo Scouts. The U.S. Sixth Army was a little out of its environment in the Pacific with more water than land to work with. Lt. Gen. Walter Krueger decided he needed recon soldiers to help even the odds, and formed the Alamo Scouts. The soldiers trained in weapons, communications, amphibious reconnaissance, and more.

But no entity or unit in WWII was more secret than the Office of Strategic Services. The forerunner to the CIA, the OSS was created in June 1942 and performed both intelligence gathering and operational missions. Yet, the fledgling intelligence agency also butted heads with everyone from the FBI to Army G-2 and the Office of Naval Intelligence.

The Modern Secret Units Serving the US

OSS weapons training
OSS weapons training in Area C. (National Archives)

Much has changed since the inception of special operations during WWII. From Korea and Vietnam to conflicts beyond, special operators have played crucial and secretive roles in conflicts both declared and unconfirmed.

But what is the most secret unit in the U.S. military’s arsenal? 

While SEAL Team Six and Delta Force are well-known among the public, the most secretive unit belongs to the CIA. Or maybe it belongs to the Army? Speculation varies about whom they fall under, but the Intelligence Support Activity (ISA) appears to work primarily for Joint Special Operations Command. The group has also alternatively been referred to as Gray Fox, Task Force Orange, and a host of other names.

U.S. Navy SEALs: Secret History

Read Next: U.S. Navy SEALs: Secret History

While few specifics are known, like many other units throughout history, the ISA appears to fit a specific puzzle-piece role within the special operations community. The unit appears to have existed operationally prior to the 1980s, but the group became more important following the 1980 Tehran hostage crisis.

The Most Secret Units in US Military History
Repainted Bluebeard RH-53D helicopters in sand camouflage and without markings aboard USS Nimitz. The helicopters were used in the failed effort to rescue hostages from Tehran in 1980. (U.S. Navy)

Members of ISA are purportedly recruited from within the special operations community. They receive added training in their role as special operators with a bit more of a spy’s edge.

ISA is alternatively described as providing other special operations units with intelligence and eyes-on-the-ground, and as specialists who take on roles other units can’t. They might also be involved in hostage rescue and direct action missions.