Beckwith faced a problem common to anyone trying to create something new inside a large institution: he needed time the Army did not want to give him. A British brigadier named John Watts had quietly advised him in 1976 that an honest estimate was eighteen months, but to tell Army leadership it would take two years - and not to let anyone talk him down. To justify the timeline, Beckwith and his small staff drafted a document they nicknamed the Robert Redford Paper, laying out the necessities and historical precedents for a four-phase selection and assessment process. On November 19, 1977, Delta Force was formally established, with Beckwith and Colonel Thomas Henry at the helm. In the gap before Delta was ready, Colonel Bob "Black Gloves" Mountel of the 5th Special Forces Group stood up a stopgap unit called Blue Light. The first Delta selection course ran from April to September 1978. By the fall of 1979, the unit was certified fully mission capable. Six weeks later, students stormed the U.S. embassy in Tehran.

On April 24 and 25, 1980, Delta operators staged at a remote desert airstrip in Iran code-named Desert One. The plan was audacious: helicopter to a hide site, infiltrate Tehran, free 52 American hostages, exfiltrate by air. The plan died on the ground. Mechanical failures grounded helicopters before the assault force ever reached the embassy. Worse came during the withdrawal, when a helicopter and a C-130 collided on the desert floor. Eight American servicemen were killed in the explosion. Operation Eagle Claw was aborted. The hostages remained captive for nine more months. The political and human cost was immense, but the operational lessons reshaped American special operations. The 160th Special Operations Aviation Regiment - the Night Stalkers - was created so dedicated aviators would fly these missions. Joint Special Operations Command was established to coordinate the various counter-terrorism units. SEAL Team Six was created for maritime work. Almost every piece of the modern American special operations enterprise traces back, in some way, to what went wrong on that Iranian airstrip.

Thirteen years after Desert One, operators from Delta's C Squadron were on the ground in Somalia for Operation Gothic Serpent. The mission was to capture lieutenants of warlord Mohamed Farrah Aidid. On October 3, 1993, what should have been a 30-minute raid extended into a nightlong battle through the streets of Mogadishu after Somali militiamen shot down two Black Hawk helicopters. Master Sergeant Gary Gordon and Sergeant First Class Randy Shughart - both Delta operators - asked three times for permission to be inserted at the second crash site, knowing what they were volunteering for. They were granted permission on the third request. They held off attackers long enough to pull pilot Michael Durant from the wreckage. Both Gordon and Shughart were killed defending him. Both were posthumously awarded the Medal of Honor. Eighteen Americans died in the battle. Mark Bowden's book Black Hawk Down and Ridley Scott's film made what Delta does, and what it costs, more public than the unit had ever been before.

Delta is headquartered at Fort Bragg, North Carolina, though almost everything else about it is classified - missions, exact unit strength, even the names of operators. Selection runs twice a year at Camp Dawson in the West Virginia mountains. The course famously culminates in The Long Walk: a 40-mile rucksack march over rough terrain with no announced time limit, the candidate told only to keep moving until told to stop. Former operators have described attrition rates above 90 percent. Those who pass enter the six-month Operator Training Course, where they learn marksmanship at close quarters, breaching, sniper fieldcraft, tradecraft borrowed from the CIA, and protective driving developed with the Secret Service. Relaxed grooming standards - beards, civilian haircuts - exist so operators can blend in overseas. The unit deployed to Grenada in 1983, Panama in 1989, and was awarded Presidential Unit Citations for combat in Afghanistan and Iraq. On October 26, 2019, Delta operators conducted the raid that ended Islamic State leader Abu Bakr al-Baghdadi. Most of what they do, the public never learns about. That has always been the point.