Kabul, Afghanistan (CNN) The sound of a bare razor, scraping hair off an unwashed scalp. The shuddering foot of someone struggling with the agony of withdrawal. The endless racks of expensive internet cables that once connected the building to satellites in space but now gather dust.

Months ago, this was Camp Phoenix.

A large and tidy NATO military base, it was home to hundreds of British soldiers and their support staff, and some Americans too.

CNN used to visit for often highly organized media events that NATO laid on in a bid to show the war in Afghanistan was being won, and they could go home. But now victories here are a little more palpable, and something that everyone inside the base's walls can only win over themselves.

Poppy country

JUST WATCHED Afghanistan's TOLO TV defies the Taliban Replay More Videos ... MUST WATCH Afghanistan's TOLO TV defies the Taliban 02:47

Camp Phoenix has been turned into a large and heavily fortified drug rehabilitation center. Walls that once kept the Taliban's bombs out, now keep those struggling with heroin addiction in.

Heroin is a shocking blight on Afghanistan, one bolstered by the country's endless supply of cheap opium. The country's most lost and dejected find solace in what is perhaps its most famous export, if not its deadliest.

There are 1.9 to 2.4 million adult drug users in Afghanistan, according to the United Nations, or around 12.6% of the adult population -- more than double the global drug use rate of 5.2%.

Opium harvested in Afghanistan -- 3,300 tonnes in 2015, according to the UN (the same as in 2000) -- is also increasingly making its way to the U.S., itself in the midst of a heroin epidemic.

Drug addicts exercise at a rehab center in Kabul.

Personal wars

JUST WATCHED One city's radical fix for heroin epidemic Replay More Videos ... MUST WATCH One city's radical fix for heroin epidemic 03:43

Patients are voluntary, except when they're not.

Either families drop them off, exhausted at looking after them, or the police sweep the streets, and one particularly notorious bridge on the outskirts of Kabul, and dump their haul of human cargo at the center.

Occasionally a patient, like Wais, will stumble in of their own volition.

Wais is 45, and just beginning his journey of rehabilitation, his eyes dazed, sparkling with panic about the ungovernable sensations beginning to grip his body.

The center doesn't do soft landings, there's no methadone here -- the drug most often used in the West to ease withdrawal symptoms -- just the occasional anti-depressant, and lots of cold turkey.

First, patients heads are shaved. Perhaps for hygiene, or perhaps to remind them that this is a new phase of their lives.

Young drug users in Afghanistan.

No lather, no electric trimmer, just a bare disposable razor sweeping off Wais' thick, dark hair. Five minutes later he is beardless, bald and sits dizzily waiting for a medical examination.

Already the symptoms of withdrawal are kicking in, "I have pain all over my body and I feel so exhausted that if I had a knife I would cut myself apart."

Sometimes the pain is so great, says Dr. Dariush Osmani, the center's deputy director, that patients attempt to set fire to their rooms.

Others have used internet cables lining the ceiling to try and hang themselves. Withdrawal makes there seem like there is no alternative.

Osmani recounts the endless schemes addicts use to smuggle heroin into the center: hidden in oranges, in people, thrown over the wall. But he says the biggest danger comes from dealers themselves, who see the center as a threat to their business.

Yet inside these walls, the exorbitant cost of the NATO campaign in Afghanistan, where multi-million dollar facilities like this would appear and disappear in months in service of endlessly changing goals, there is some comfort that a weapon of war is now a tool of healing for the country's most frail.