The US Army, Navy, Air Force and Coast Guard -- along with many foreign militaries -- all already accommodate the religious requirements of Sikhism, the faith born five centuries ago in South Asia that forbids men from cutting hair or trimming beards and requires turbans.

But the Marine Corps, responding to three Sikhs who passed tests to enlist last year, refused to make exemptions to grooming rules during 13 weeks of basic training and during potential periods of combat, although the three could maintain their beards and turbans at other times.

The Marine leadership argued that recruits needed to be "stripped of their individuality" as part of a "psychological transformation" toward shared sacrifice, according to the ruling.

A three-judge bench of the US Court of Appeals in Washington disagreed, saying the Marines did not present any argument that beards and turbans would affect safety or physically impede training.

The court noted that the Marines exempted men with razor bumps, a skin condition, from shaving, allowed women to maintain their hairstyles and largely permitted tattoos -- "a quintessential expression of individual identity."

"If the need to develop unit cohesion during recruit training can accommodate some external indicia of individuality, then whatever line is drawn cannot turn on whether those indicia are prevalent in society or instead reflect the faith practice of a minority," said the decision written by Judge Patricia Millett, who was nominated by former president Barack Obama.

The court also pointed out that regulations on beards date only from 1976, with hirsute Marines posing no issue from the Revolutionary War to the modern period.

While military practices can evolve, any claim of "inflexible necessity" cannot "completely ignore past practice," the decision said.

The court issued a preliminary injunction to allow two of the recruits, Milaap Singh Chahal and Jaskirat Singh, to begin training with their articles of faith while a district court more fully weighs the case.

The appeals court also backed the merits of the case of the third plaintiff, Aekash Singh, but said he appears to have delayed enlistment.

Giselle Klapper, a senior staff attorney at the Sikh Coalition advocacy group, hailed the ruling, saying it meant that "faithful Sikhs who are called to serve our country can now also do so in the US Marine Corps."