The 1st Special Forces Operational Detachment-Delta (Airborne) —1st SFOD-D (A)— also known as Delta Force, is a Special Operations Force (SOF) of the United States Army Special Operations Command (USASOC). The force's main purpose is counter-terrorism, although the force is extremely versatile. Delta Force is believed to conduct missions similar to those regularly attributed to the British SAS (Special Air Service), the U.S. Navy's DEVGRU, Germany's GSG-9, France's GIGN, and other elite counter-terrorism forces worldwide.

Background
The Pentagon controls information about Delta Force tightly and publicly refuses to comment on the secretive unit. Initially, the existence of Delta Force was officially denied, even though it was commonly known that the unit took part in Operation Eagle Claw, the failed attempt to rescue American hostages from the U.S. Embassy in Iran in 1980.

By the 1990s the existence of Delta Force was obvious, as the U.S. military started to officially post messages around their bases regarding Delta Force recruitment, by using their official force name: 1st SFOD — although the U.S. military has never released any official fact sheet of the force.

In 1999, writer Mark Bowden published the book ‘Black Hawk Down: A Story of Modern War’ which chronicles the events that surrounded the October 3, 1993 Battle of Mogadishu. The book, in a short brief, relates Delta Force's involvement in the operations that occurred before the events leading to the battle. The book was later turned into a film by director Ridley Scott in 2001.

Operations
Delta Force sub-divides into three operating squadrons, each of which comprises small groups known as "troops". Each troop specializes in HALO/HAHO, SCUBA, or other skill groups. They can each further divide into smaller units, as needed to fit mission requirements.

In addition, one of the likely components of Delta Force is the epithetically named "Funny Platoon". Allegedly, it consists only of women, being the only part of the U.S. special operations community that accepts them. It is alleged that the unit's members are intended to be deployed alone rather than in groups, since there are some locales where women would arouse less suspicion than men. For this reason, the tactics of its members are said to emphasize the use of disguises and concealable small arms. It is not known whether any members of the "Funny Platoon" have been involved in Delta Force operations to date.

Delta Force is also known as the Combat Applications Group (CAG).

Recruitment and training
Contrary to popular belief, Delta Force recruits its members solely from the Army, usually from the Army Special Forces (Green Berets) and the Rangers. Their main compound stands in a remote area of Fort Bragg, North Carolina and houses about 2,500 personnel. Reports of the compound mention numerous shooting facilities (both for close-quarters battle and longer-range sniping), a dive tank, an Olympic size swimming pool, a huge climbing wall, and a mockup of an airliner.

Potential Delta Force operatives undergo an extremely tough training regime, basically a combination of the Q-course and SAS selection. Candidates must pass two phases in order to become a Delta operative. The first phase consists of physical training; candidates must score 70 on each of the events and most candidates will pass this event without any trouble. 

In Stress Phase, candidates undergo several route marches carrying 65 pounds or more (if a cadre member catches a candidate cheating then he will carry more weight) of gear, and a weapon. These marches are similar to the SAS selection trials; candidates must reach certain checkpoints in a certain amount of time, known as "point to point". During several of the long marches, candidates must answer examination questions, ranging from "Who would you consider to be the strongest leader" to "Who would you choose as a team member". This tests the candidates mental capacity and awareness. The final examination of Stress Phase is a 40 mile march carrying 80 pounds, which must be completed in 20 hours. After completing stress phase, candidates are tested on their agressive nature and how well they can handle themselves while facing an interrogator. Finally, candidates appear before the commander's board, where they are aggressively questioned. Candidates who are selected then undergo further training.

Delta Force in modern conflicts.
One of several operations in which Delta Force operators played important roles was the invasion of Iraq in 2003. [8] (PDF document) They allegedly entered Baghdad in advance, along with SEALs from DEVGRU, building networks of informants while eavesdropping on and sabotaging Iraqi communication lines. There is also a rumor that Delta Operatives and Navy SEALs had infiltrated the country prior to the invasion and planted explosive devices on key buildings and blew them up when the air raids began.

In addition, the force was involved in the offensive against the Taliban in Afghanistan in 2002. [9] In particular, many observers strongly suspect that members of Delta Force made up one of two units involved in a raid on a residence belonging to Mullah Omar. According to The Pentagon, the level of resistance to that operation was minimal.

The Mullah was not present, but some papers and computer disks were said to have been seized in the raid. Critics later alleged that the second unit was unnecessary, claiming that it was very large and uncoordinated. As a result, they say, the defenders were alerted early and the number of friendly casualties was in fact higher than reported. According to the book Shadow Wars, Delta Operatives wanted a quiet insertion method that was denied and command opted for a combined Ranger Assault, apparently Taliban fighters ambushed the team when they were extracting and several Delta Operatives were severely wounded.