During the Vietnam War, the US created a highly classified unit that still influences modern special operations

• As the US waged a conventional war in South Vietnam, a group of special operators carried out a secret war inside and outside the country.
• The Military Assistance Command Vietnam-Studies and Observations Group, as their unit was known, was disbanded after the war, but it had a lasting influence on modern US special operations forces.

As the US's involvement in Vietnam steadily grew with more conventional troops, so did its secret war.

To counter the Viet Cong's guerrilla campaign, supported by the North Vietnamese army (NVA), raging inside South Vietnam, the Pentagon established a highly secretive special operations organization in 1964.

The Military Assistance Command Vietnam-Studies and Observations Group (MACV-SOG) was tasked with taking the fight to the enemy regardless of where they were. Cross-border operations in Cambodia, Laos, and North Vietnam-where US troops weren't supposed to be-became SOG's specialty.

Special-operations pioneers

Composed of Green Berets, Navy SEALs, Recon Marines, Air Commandos, and their indigenous allies, SOG primarily conducted reconnaissance and direct action operations, such as ambushes, in South Vietnam and across the border.

Cross-border recon missions often led to epic gunfights, as the small SOG teams would be compromised and hunted down by devastatingly superior enemy forces. It was more common than not for a recon team to be extracted under fire and with their perimeter minutes, if not seconds, away from being overrun.

"SOG operations hurt the NVA [and] impeded the shipment of supplies/soldiers south on the Ho Chi Minh Trail," John Stryker Meyer, a legendary SOG operator, told Insider.

"There were also major intel coups. For example, Operation Tailwind, which saved the CIA in Thailand, produced troves of key NVA intel. There was also Bargewell, who found valuable intel on an NVA base camp despite having been shot in the chest," Meyer added, referring to Eldon Bargewell, who went on to be a renowned general and commander in the Army's Delta Force.

Just one day with SOG could produce a lifetime of stories. For Meyer, a veteran of two SOG deployments who has written about his hair-raising experiences, it was hard to pick the most notable moment. Despite a late-night and personal encounter with an NVA soldier in the field, Meyer's most memorable operation was when his recon team went against three NVA divisions - 30,000 men - Thanksgiving Day.

In the end, the US lost the war despite the herculean efforts of SOG and its contribution to the fight.

"There were contributions that we never learned about. For example, we pulled off a few wiretaps [in the Ho Chi Minh Trail], but we never heard back from the CIA on results," Meyer said. "Getting honest answers from the Communists about SOG's impact is impossible, but you take a case like October 5, 1968, when Recon Team Alabama and its air assets were responsible for 9,000 enemy troops KIA or WIA-that had an impact on troops moving south."

As direct US involvement in the war shrank, SOG became less needed, and in 1972, it was deactivated.

"Like anything else, politics interfered. Our command structure often had to fight to keep close air support units assigned to support SOG, such as the A-1 Skyraider support," Meyer said of why SOG wasn't kept after Vietnam.

But SOG alumni continued to serve, which would prove key for the future of US special-operations forces.

Paving the way for JSOC

Eight years after MACV-SOG was deactivated, the Pentagon was forced to create a similar organization.

Joint Special Operations Command (JSOC) was born after the failure to rescue the American hostages from Iran during Operation Eagle Claw.

Col. Charlie Beckwith, the founder of Delta Force and ground force commander during the mission, argued for a joint command that would bring together America's special operators. Beckwith had served in SOG and thus already had an idea of what such a command could look like, despite the enemy now being terrorists and not the NVA.

As a result, the Pentagon created US Special Operations Command, its subordinate service commands, and JSOC.

JSOC contains the military's tier-one units and is considered a national strategic asset. Initially, Delta Force and SEAL Team 6, which were JSOC's counterterrorism direct-action units, were predominately manned with Vietnam veterans, several of whom had served in SOG.

Although the conditions under which JSOC was created were completely different from those in which SOG worked, they share lots of similarities.

Both organizations are joint, meaning that their units came from across the military and not just from one service. Additionally, they focus on both covert and clandestine operations. They also share a close relationship with the intelligence community, often working directly for it, like on the Osama bin Laden raid, during which the SEAL Team 6 operators were nominally under CIA control.

There are divergences as well. A significant difference between the two organizations-and between the times in which they fought-is their relationship with risk.

SOG leaders and operators didn't hesitate to take an extreme risk in their fight against the North Vietnamese. Indeed, several SOG operations could be considered suicidal.

Whether it was when a SOG team went after three NVA divisions or when a reinforced SOG company went deep into Laos to help the CIA, SOG operations were characterized by their high-risk level. That was reflected in SOG's 100% casualty rate, meaning every operator was either wounded, often multiple times, or killed.

Conversely, today there is a risk-averse culture, even in the most elite special-operations organizations.

"You can't even enter the room if you carry a CONOP [concept of operations] similar to SOG's," a former Delta Force operator told Insider. "There is no way anyone would approve that today."

"The SAR window plays a big part in that," the Delta operator said, referring to the military's requirement that troops - commandos or not - be within range of a search-and-rescue asset in case their mission goes south.

"But, to be fair, it's a very different environment. We aren't engaged in a major war like Vietnam, and our organizations are different. We're the national mission force. We can't afford the casualty rate these guys had."

SOG operators agree with that view.

"Every spec-ops operator I've met in recent years from today's conflicts all agree that many of the missions we ran would never be allowed today due to threat levels," Meyer added.

In the end, policy limitations notwithstanding, JSOC is continuing SOG's special-operations legacy.