British army/Imperial War Museum The Special Air Service is the longest active special missions unit in existence and has remained one of the best. Staffed with the toughest and most resourceful enlisted and commissioned soldiers the United Kingdom has to offer, the SAS only accepts the cream of the crop. Of all candidates who try to earn the coveted beige beret and the title of "Blade," only the very best make it through. In order to thin out the herd, the SAS holds one of the most arduous and rigorous selection and training programs in the modern special operations community.