The Red Crescent has an incentive to claim neutrality; at stake are hundreds of millions of dollars of international aid that opposition leaders in exile are trying to divert from the organization to their own aid groups or to international agencies they say would be more impartial.

But international aid workers say the group’s evolution also appears to be driven by new volunteers, starved for meaningful civic action, who take the mission of serving all sides seriously. Volunteers coordinate with security forces and rebels to cross battle lines. Permission is often denied, and when it is granted it does not equal protection.

One Damascus squad leader, accused of supplying armed groups in Zabadani, near Damascus, spent 75 days in prison. He lost 88 pounds and had to undergo reconstructive surgery on a leg in Switzerland “because of the good treatment he faced,” a volunteer said sarcastically, speaking on the condition of anonymity for fear of retribution.

Asked about such cases, the volunteer let out an acid chuckle.

“We are guilty,” he said, of treating and feeding people some officials say they “want to kill.” The Red Crescent, he explained, gives supplies to civilian committees in rebel-held towns, without tracking where they end up.

In the break room, nearly all the volunteers — students of pharmacy, music and French literature — said they had been at least briefly detained. They fretted about one squad, arrested that morning en route to a clinic in the contested neighborhood of Jobar. Just then, the missing crew burst into the room, newly released, still in their red uniforms.

Colleagues leapt to hug them, shouting, “Thank God for your health!”

Moments later, a bell rang. One recent detainee, an actor in his former life, rushed out for a mission, chewing a sandwich and pumping his fist like a champion.