In good Sikh tradition, he resisted. Armed with petitions and Congressional letters, he waged a two-year campaign that in 2009 resulted in the Army granting him a special exception for his unshorn hair, the first such accommodation to a policy established in the 1980s.

Since then, two other Sikhs have won accommodations from the Army. But many others have failed. And so now, as he prepares to leave active duty, Major Kalsi, who earned a Bronze Star in Afghanistan, is waging a new campaign: to rescind those strict rules that he believes have blocked hundreds of Sikhs from joining the military.

“Folks say, ‘If you really want to serve, why don’t you cut your beard?’ ” said Major Kalsi, a doctor who is the medical director of emergency medical services at Fort Bragg in North Carolina. “But asking a person to choose between religion and country, that’s not who we are as a nation. We’re better than that. We can be Sikhs and soldiers at the same time.”

He makes a compelling point. The new army is much more flexible than the old army.