The unit's missions primarily involve counterterrorism, hostage rescue, direct action, and special reconnaissance, often against high-value targets.

Delta Force, along with the Intelligence Support Activity, and its Navy and Air Force counterparts, DEVGRU (SEAL Team 6) and the 24th Special Tactics Squadron, are the U.S. military's tier one special mission units that are tasked with performing the most complex, covert, and dangerous missions directed by the president of the United States and the secretary of defense.

[11][12] Delta Force was created in 1977 after numerous well-publicized terrorist incidents led the U.S. government to develop a full-time counter-terrorism unit.

[13] He envisioned highly adaptable and completely autonomous small teams with a broad array of special skills for direct action and counter-terrorism missions.

He briefed military and government figures, who were resistant to creating a new unit outside of Special Forces or changing existing methods.

Watts had made it clear to Beckwith that it would take eighteen months to build a squadron, but advised him to tell Army leaders that it would take two years, and not to "let anyone talk (him) out of this."

To justify why it would take two years to build Delta, Beckwith and his staff drafted what they dubbed the "Robert Redford Paper," which outlined its necessities and historical precedents for a four-phase selection/assessment process.

[17] In the meantime, Colonel Bob "Black Gloves" Mountel of the 5th Special Forces Group created a unit to bridge the short-term gap that existed until Delta was ready, dubbed Blue Light.

[18] The initial members of the unit were screened from volunteers and put through a specialized selection process in early 1978, involving a series of land navigation problems in mountainous terrain while carrying increasing weight.

The Navy's SEAL Team Six, an earlier incarnation of the current Naval Special Warfare Development Group, was created for maritime counter-terrorism operations.

[22] Naylor further details Delta Force's structure in his book Relentless Strike: The Secret History of Joint Special Operations Command.

Haney wrote that the course began with standard tests including push-ups, sit-ups, and a 2-mile (3.2 km) run, an inverted crawl and a 110-yard (330 ft; 100 m) swim fully dressed.

The candidates were then put through a series of land navigation courses, one of which required them to travel 18 miles (29 km) at night while carrying a 40-pound (18 kg) rucksack.

The final challenge was a 40-mile (64 km) march with a 45-pound (20 kg) rucksack over rough terrain that had to be completed in an unknown amount of time; this was also colloquially known as "The Long Walk".

[34][35] Former Navy SEAL, DEVGRU and Delta operator Kevin Holland stated that in his selection class 120 candidates started, 16 passed and eight finished OTC.

[1] Relaxed grooming standards such as civilian hairstyles and facial hair are allowed to enable the members to blend in and avoid recognition as military personnel.

[48] In Veritas, the Journal of Army Special Operations History, Charles H. Briscoe stated that "SF did not misappropriate the appellation.

[50] On 26 October 2019, Delta operators accompanied by members of the 75th Ranger Regiment conducted a raid on the compound of Islamic State leader Abu Bakr al-Baghdadi, leading to his death.