Just how much torture is a person willing to undergo to get a prestigious job? Given that an average of 250 resumes are submitted for every job position in the United States, one would assume quite a lot.

But there’s writing endless resumes—and then there’s running forty miles at night on an uneven forest trail while lugging a fifty-pound rucksack—with more weight added upon achieving each waypoint.

And to even get into the application pool for that particular job, you first have to master the art of willingly jumping out of a perfectly functional airplane.

This refers, of course, to the admission process for the U.S. Army’s top commando unit.

Eric Haney described the experience of one of the long-distance hiking in his book Inside Delta Force:

“I had covered just slightly over thirty miles by now, but still had more than twenty to go. It was getting more and more difficult to do speed computations in my head. My hands were tingling from the rucksack straps cutting into my shoulders, pinching the nerves and arteries, and restricting the blood flow to my arms.

I was bent forward against the weight of the rucksack. It felt like I was dragging a train behind me, and my feet hurt all the way up to my knees. I don’t mean they were just sore, I mean they felt like I had been strapped to the rack and someone had beaten the balls of my feet with a bat. I tried to calculate the foot-pounds of energy my feet had absorbed so far today, but I had to give up the effort. I only knew that the accumulated tonnage of all those thousands of steps was immense. And it was only going to get worse.”

Special Forces Operational Detachment Delta—or “Delta Force”—remains cloaked equally in official secrecy and popular legend. 

Technically an elite counter-terrorism Special Missions Unit, Delta Force has been involved in virtually every major U.S. military action since the 1980s—whether attempting to rescue political prisoners from a fortified prison in Grenada, nabbing Panamanian strongman Manuel Noriega, hunting Scud missiles behind Iraqi lines, battling Somali warlords, assassinating ISIS leaders, and even assisting Mexican marines in a deadly gun battle that saw the capture of drug kingpin “El Chapo.” 

And one can only speculate about all the missions that remain classified.

The unit’s existence remains ritually unacknowledged by the U.S. government, despite its organization and aliases (a common one is “Combat Application Group” (CAG)) being reasonably well-documented in books by former members and its exploits celebrated in movies like Black Hawk Down and television series like The Unit.

Delta Force was founded by Colonel Charles Beckwith, who had served in the 1960s as an exchange officer with the British Special Air Service while it was engaged in a grinding but successful counterinsurgency campaign against Communist guerillas in Malaysia.

Beckwith was one tough cookie. During his stint commanding SAS troops in the jungle, he nearly died from a bacterial infection. Then, while commanding Green Berets in Vietnam he was struck by a .50 caliber slug—and survived after being triaged as a lost cause.

These experiences left their impression on the Georgia native, who went on to devise the rigorous “Q-Course” used to train the Green Beret special operations forces of today.

Beckwith was convinced the Army needed an even more elite direct action unit with the mental and physical fortitude to operate independently at length in the field. Furthermore, he emphasized that unit should only be composed of experienced officers and non-commissioned officers (NCOs) who had already proven their skills in the field.

Today, Beckwith’s vision still informs Delta Force’s selective training regimen. To even qualify for the Delta Operator Training Course (OTC), Delta recruits must possess years of experience, with qualification for parachute operations, a “Secret” security clearance, and a clean disciplinary record.

Reportedly, these requirements mean that three-quarters of Delta Force recruits are sourced from the Army’s two other primary Special Operations units: the 75^th Ranger Regiment—which often engages in larger-scale operations behind enemy lines—and the Green Berets, who specialize in embedding with, training and leading local forces in foreign countries.

The Operator Training Course itself places heavy emphasis on perfecting marksmanship—especially in hostage-rescue contexts. Several facilities are maintained solely to practice hostage rescue scenarios in realistic environments ranging from large civilian buildings, to airliners and warships.

Delta trainees also receive instruction in demolitions, lock-picking and even bomb-making techniques. They are trained by CIA operatives in espionage techniques from shadowing persons of interest to transmitting intelligence via dead drops and even aggressive “tactical driving”—yes, the kind you thought was only a fantasy reserved for action movies.

Only a fraction of those selected to undertake the OTC manage to complete it.

Obviously, it takes a rare individual to muster the physical endurance, mental adaptability and sheer ambition to first qualify and then complete the six-month Operator Training Course.

But there’s also a sobering sub-text to the extreme training regimen: Delta Force has historically often been called upon to perform missions with a high risk of failure.

Operation Eagle Claw, the only Delta mission led by Beckwith, was an attempt to rescue hostages at the U.S. embassy in Iran in 1979. It ended in flames before even encountering enemy forces when one of the helicopters involved crashed into the tanker it was refueling from, killing eight.

In October 1993, Delta snipers Randy Shughart and Gary Gordon Delta hopped off an orbiting helicopter, having insisted they need to insert on the ground to save crashed Army helicopter pilot Michael Durant from a besieging mob in the streets of Mogadishu, Somalia. Both were killed minutes later, along with three other Delta operators who perished in a day-long battle that left roughly a thousand dead.

During the early years of the hunt for Bin Laden, Delta operators saw action in Afghanistan—at one point coming to the rescue of Afghan President Hamid Karzai after he was nearly killed by an errant laser-guided bomb—and more discreetly in Pakistan and India’s Kashmir province. They also participated in numerous raids during the invasion of Iraq and the lengthy counterinsurgency conflict that followed. Near the end of the U.S. mission in Iraq in 2009, the Washington Post reported roughly half of all Delta operatives in Iraq had received Purple Hearts for being injured in combat.

In this light, the unit’s brutal selection and training process is revealed to have a purpose beyond physical fitness fetishism—it’s to help identify the kinds of individuals with the physical prowess and motivation to repeatedly undertake dangerous missions which may indeed at times prove to be impossible.

Sébastien Roblin holds a master’s degree in conflict resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring.