1st Special Detachment Delta, or Delta
Force, is a secret Counter Terrorism Branch of the US
Army. They specialize in Hostage Situations, Recon Missions, and Counter Terrorism. Contrary to what Camoking wrote, Delta did not
fail while attempting to rescue hostages, it was in fact the Air
Force that failed. Delta had to be pulled out before they started their mission because of the Air Force's lack of balls. They now have their own aviation wing known as the 160th SOAR. Also the hostages were not at the Iran Embassy in the
UK they were actually in Iran. Second, they don't
train with the SAS to hone their skills. They were formed similarly to the SAS and took their procedures and extended upon them. If you are interested in their
history read some books on the issue. One great book is Inside Delta Force by
Eric Haney. This is a terrific book filled with wonderful information about Delta by one of their founding members. What you don't do is listen to idiots that only know bits of information and get the specifics wrong.