I have considered your request for a religious accommodation to permit you to wear a beard, turban, and uncut hair in observance of your Sikh faith.... I grant your request for an exception to Army personal appearance and grooming standards, subject to the limitations described below....
While assigned or performing non-hazardous duties, you may wear a beard, turban, and uncut hair in a neat and conservative manner that presents a professional and well-groomed appearance. The bulk or your hair, beard, or turban may not be such that it impairs your ability to wear the Army Combat Helmet ... or other protective equipment....
Because of the Army's strong interest in maintaining good order and discipline, the Army intends to develop clear uniform standards applicable to Soldiers who have received a religious accommodation. Until such standards are published, you may wear a black turban (or under turban, as appropriate)....The Memorandum goes on to specify precise hair and beard lengths, and says that Singh's commander is to provide quarterly assessments of the effect of the accommodation on unit cohesion and morale, good order and discipline, health and safety, and individual and unit readiness. West reports on the Army's action.
UPDATE: Stars and Stripes reported on April 11 that 3 additional Sikh enlistees have been granted similar accommodations.