S.A.S.
The SAS is respected worldwide and used to train many other Special Forces Units. Several special operations units are modeled after the SAS. For example, the U.S. Army's Delta Force was founded due in large part to Charles Beckwith, a U.S. Army special operations officer, serving as an exchange officer with the SAS. He felt that the U.S. Army was vulnerable in not having a unit comparable to the SAS.