However, during the wars in Iraq and Afghanistan Special Operations soldiers have had lax facial-hair regulations, and having a beard has even become a mark of elite soldiers.

This summer, a United States District Court judge rejected the safety argument, noting that more than 100,000 troops have been allowed to grow beards for medical reasons such as acne and sensitive skin. The judge ruled the Army’s denial was illegal. But the decision applied only to students enrolling in R.O.T.C., leaving the larger question of beards for active-duty troops untouched.

Sikhs say lifting the ban is particularly important to them because they have had a long history of military service. Sikhism developed in northwestern India as a religion centered on protecting the innocent and resisting tyrants during long bouts of conflict and oppression from invading Mughals and Afghans. Bearded Sikhs fought in the United States Army in World War II and Vietnam. Today, Sikhs in full religious garb serve in militaries around the world.

For centuries, Sikh teachings have required adherents to leave their hair and beard unshorn, and to wear a turban.

“It was a way to identify the Sikhs, who became a sort of military order that stood up against oppression,” said Kamaljeet Singh Kalsi, a doctor who is a major in the Army Reserve.

Major Kalsi got permission to grow a beard in 2009. He was the first of only three Sikhs to receive permission before Captain Singh. Two Muslims and a Jewish rabbi also have been granted accommodations since 2009. But all apparently served either as chaplains or in specialty medical fields, a spokeswoman for the Army said. No combat soldiers had been given a pass.

The Army has used a procedural Catch-22 to sidestep the question of whether regulations protecting religious freedom allow for beards. For years, it denied requests from incoming recruits, saying accommodations could be granted only after recruits had formally joined. Recruits could not formally join without conforming to grooming standards. In short, to get permission to not shave, you had to shave.