Mike Turner, a Republican member of the House of Representatives and chairman of its intelligence committee, wrote to Joe Biden complaining about the lack of further detail from the White House on North Korean troop movements.

“The administration has not briefed the House Permanent Select Committee on Intelligence…of any assessments by US intelligence agencies or the department of defence regarding these troop movements,” he wrote, calling for an immediate briefing on the matter.

Founded around 1968, the SOF is perhaps best known for a disastrous attempt at raiding the Blue House, South Korea’s presidential residence, that year, which ended in the death of 29 out of the 31 operatives involved. 

Unlike the SAS or Israeli Mossad, little else is known about the intelligence service’s exploits, though some of its troops took part in a rare public event in 2017 that involved marching in formation alongside regular army soldiers.

In images broadcast by North Korean state TV, SOF troops were seen wearing black camouflage paint and dark sunglasses. They also carried what state media described as a new rifle fitted with a grenade launcher, and were clad in helmets with night vision goggles.

Several news reports at the time noted a distinct similarity to the uniforms of South Korean special forces – known as the Black Berets – suggesting they may have been modelled directly after them.

A report by Maxwell Goldstein, an analyst at Grey Dynamics, the London-based intelligence consultancy, in July described the SOF as aspiring to be “highly trained troops equipped with the best gear available for dangerous but essential missions”.

He said the SOF possesses 12 light infantry brigades, three reconnaissance units for operating behind enemy lines, three airborne divisions and three general sniper units, in addition to sniper brigades attached to air force and naval forces.

The SOF’s estimated size of 200,000 men is unusual in comparison to other international special forces units. The British SAS is believed to have as few as 500 active soldiers at any given time, while the US Delta Force contains some 2,000 operating members.