The largest gathering of indigenous nations in modern American history has set up camp on land belonging to the Army Corps of Engineers at the confluence of the Cannonball and Missouri rivers in North Dakota. Tents and teepees, now home to whole families, stretch the plain.

They have come by the hundreds to protest construction of the 1,172-mile Dakota Access oil pipeline, which would run within a half-mile of the Standing Rock Sioux reservation and cross beneath the Missouri River. Opponents say the pipeline will adversely impact drinking water and disturb sacred tribal sites.

Supporters say it would enable crude oil from North Dakota to reach major refineries while reducing more dangerous rail and truck transport.

Reporter Sasha von Oldershausen spent three days with the protesters to see how they are living and to learn why they have answered the call of the Standing Rock Sioux.

NEAR CANNON BALL, N.D. — Winter is coming to the plains. At all times of the day, when there is lumber to chop, men throw their weight into axes and cut firewood for the frigid days ahead.

One tribe from Wisconsin recently visited the camp with a logging truck filled with lumber that 20 men unloaded by hand. The camp relies on these donations for its survival, and wood is scarce.

“We need to conserve our wood,” Everett Iron Eyes, a Standing Rock Lakota and camp organizer, said to people packed beneath the large, brown canopy of tent at the top of a hill. Just below, hundreds have been camping for months in protest of the Dakota Access pipeline.

“Our people survived hundreds of years in the snow,” he said, the heavy canvas walls snapping like sails from the blustery wind. Inside, all was still as people sat cross-legged or stood along the fringes. Elders occupied the few available metal fold-out chairs. Everyone was listening.

A man chops wood at the Standing Rock Indian Reservation in North Dakota on Sept. 21 as demonstrators gathered to protest the construction of an oil pipeline. Jim Seida / NBC News

“You can see the birds and animals getting ready,” Iron Eyes said quietly. “We have to, too.”

Fire is more than just a source of warmth for the camp. At night, campfires accompany a perpetual drumbeat that fades only after the voices do. Teepees glow like paper lanterns illuminated by campfires burning within. “Water is Life” is the official motto of the pipeline opposition movement, but fire is what fuels its resolve.

“I see some of you making big fires that you sit around late into the night,” he said. “We can’t be doing that.”

Meanwhile, a different admonition about fire was addressed at dinner one night by another Lakota man named Cedric, who serves as the camp’s unofficial emcee. He criticized the firekeepers for nearly extinguishing the “sacred fire” stoked in the ceremonial area, a circular clearing framed by tent structures that make up the main kitchen.

“In our tradition, when the sacred fire goes out, we pack up and leave,” Cedric said, walking slowly around the fire pit. “We have to keep the flame burning.”

A 12-top burner gifted by the American Rainbow Rapid Response to the main kitchen is the source of another emblematic and perpetual flame. The non-profit organization, which provides disaster relief, had operated the very same burner in relief efforts for Hurricane Katrina and Superstorm Sandy. Nantinki Young, who manages all seven of the camp’s kitchens, responsible for feeding hundreds of people, three times a day, said the burner came just in time. Now, she can address other urgent needs.

Protesters demonstrate against the Energy Transfer Partners' Dakota Access oil pipeline near the Standing Rock Sioux reservation in Cannon Ball, North Dakota, U.S. September 9, 2016. ANDREW CULLEN / Reuters

“The challenges I face the most are making sure that we get enough food distributed,” she said. “We’re starting to run out of meat.”

One afternoon, several people stood before a table to clean the meat off the ribcage of a freshly felled buffalo donated to the camp. That night, the kitchen staff served a soup of hominy, corn and buffalo heart. On the side, a small sliver of its rich liver was offered with each bowl.

Cold coming, but ranks swell

In spite of the impending cold, the opposition has grown. At the main camp, organizers estimate more than 700 people are living in their shelters and vehicles. When the “weekend warriors” arrive, some say the numbers are in the thousands.

Still, it’s difficult to ascertain an exact number, which is the reason why a census committee was formed. Knowing their numbers would mean being able to more accurately address their needs.

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“You see those flags,” said one Lakota man, pointing to the perimeter of the main encampment. “There used to be six of them. Now, there are more than 200.” The flags are symbols of the number of indigenous nations, members of whom have either visited the encampment or else sent flags in solidarity.

Members of the REDRUM motorcycle club ride near the Standing Rock Indian Reservation in North Dakota on Sept. 21 to protest the construction of an oil pipeline. Jim Seida / NBC News

But these are not the only flags that fly here. A Palestinian flag flies just yards opposite a rainbow flag symbolizing the LGBTQ movement. Indeed the protest movement has drawn supporters from across the country and the globe, from indigenous peoples and beyond.

Despite the sprawl of the camp, things run surprisingly smoothly, thanks to a constant stream of donations and volunteers. With alcohol and drugs banned — “This is a prayer camp,” one is frequently told — there’s not much else to do but pitch in.

The camp functions as a small township, with all basic needs and services supplied by the people who reside there. By dawn each day, the banks of portable toilets had already been cleaned, and the general state of the encampment was overall much tidier than your average Lollapalooza campground. (Camp organizers highlight the importance of keeping a clean camp. “Anything they can use against us,” Iron Eyes said, referring to the pipeline company, “they will.”) Separate tents designate the doctors from the herbalists from the lawyers. There’s even a school.

For the most part, the protesters use alternative energy sources where they can. A semi trailer that functions as the main kitchen’s refrigerator is powered by donated solar panels. That might not be the case when the cold and dark winter months come, Young said. But that’s what the back-up generators are for.

The camp has been inundated with clothing donations, some of which got ruined with rot due to recent wet weather. Now, camp organizers are focusing their energy on acquiring winter-hardy provisions, like cold-weather sleeping bags and tarps. They even have an Amazon wish-list that includes lanterns, tires and two-way radios.

Iron Eyes enlisted campers to 21 committees in preparation for the long winter months ahead. Among these was a cultural committee, responsible for organizing events like a canoe contest to boost morale.

Protests lead to arrests

The opposition has encountered its fair share of obstacles. Earlier this month, protesters faced off against the pipeline company Energy Transfer Partners, which had begun to bulldoze upon a sacred tribal burial site not technically on reservation land but along the path of the proposed pipeline.

Protesters climbed the property line fence, marched along the path carved by the bulldozers, and squared off with security officers who had come equipped with dogs and pepper spray.

“Democracy Now” host Amy Goodman captured the melee on camera as some of the protestors who confronted the pipeline’s security were charged at with dogs. Others were pepper-sprayed. Many of the protesters who appeared in Goodman’s video were later arrested on grounds of trespassing on private property. Goodman herself faces criminal trespassing charges.

Hundreds of people, mostly Native Americans, gather near the Standing Rock Indian Reservation in North Dakota to protest the construction of an oil pipeline on Sept. 21. If completed, the Dakota Access Pipeline would transport 470,000 barrels of crude oil each day from North Dakota to Illinois. Jim Seida / NBC News

Federal, state and local law enforcement have also mobilized in reaction to the protest. On the two-lane highway that led to the main camp, six National Guard officers man a temporary checkpoint some 15 miles away from the encampment. “Are you aware of the situation up ahead?” they ask, before letting drivers pass through.

At the camp’s “lawyer tent,” where a handful of attorneys have offered pro bono legal counsel to the opposition, one attorney from Portland, Oregon, estimated in late September that as many as 60 arrests had been made in association with the pipeline opposition. At least several more have been made since.

Answering the call

The medical tent is staffed by a handful of rotating registered nurses, medics and doctors, who provide basic care and over-the-counter drugs. An ambulance from the Standing Rock reservation stands by. One nurse, Deedee, commutes on horseback to different encampments, providing health education to residents, and identifying the handful of pregnant mothers-to-be among them.

“We have several wonderful midwives who are here,” said Vanessa, a medic, who resides full-time at the camp. “We have a midwife here who has a Doppler, so we’ve done baby checks with a little Doppler.”

Dakota Access Pipeline protesters square off against police between the Standing Rock Reservation and the pipeline route outside the little town of Saint Anthony, North Dakota, U.S., October 5, 2016. STRINGER / Reuters

The tent had a constant flow of patients as the staff also prepared for winter. “We’ve gotten several boxes already of cold and flu symptom relief, allergy relief, headache relief, all sorts of GI relief,” said Herman Brar, 26, a registered nurse from Montana, who now splits his time between a hospital 450 miles away in Billings and the Standing Rock protest.

Dr. Jesse Lopez, 53, an Apache trauma and general surgeon from Kansas City, spent five days providing medical assistance and working on a donation of a handful of solar panels to the camp.

“There’s great organization here,” he said. “When you get this many people out in a particular area, with potential help so far away, to have eyes and hands on the ground is very important,” he added. “When I got here, there were already a lot of medicines available to those who might need it.”

Like many here, Lopez’s reasons for coming were personal. “I think a lot of people think it’s time to do what is right by the indigenous of this country because we’ve not done that and we know that. As an American people, we’ve not done that.”

“I think what’s different about this is that you have mothers and fathers and grandfathers who’ve never done anything like this before, like myself,” he said. “I’ve never done anything like this. Nor would I have thought that I would do anything like this.”

'They want to kick some ass'

The Standing Rock protest has grown beyond opposition to the pipeline or the fight for clean water.

“This is an international movement for all indigenous people,” said Awwad Yasin, a Palestinian-American law student from California, who came to the encampment with members of the Palestinian Youth Movement. “The power of will is something that can’t be understated.”

The students set up camp beside a Palestinian flag that had been raised on the camp even prior to their arrival. One thing that surprised him, he said, was that the indigenous populations seemed better informed about the Israeli-Palestinian conflict than most Americans he knows. They recognized the keffiyeh — the black-and-white patterned scarf — he wore around his head not as a fashion accessory, but as a symbol of resistance.

Supporters of the Standing Rock Sioux Tribe rally in opposition of the Dakota Access oil pipeline in front of the White House, Tuesday, Sept. 13, 2016, in Washington. The company developing the $3.8 billion Dakota Access pipeline says it is committed to the project, despite strong opposition and a federal order to halt construction near an American Indian reservation in North Dakota. (AP Photo/Jacquelyn Martin) Jacquelyn Martin / AP

Yasin and his group camped beside a teepee, where a 48-year-old Standing Rock Lakota called Unpa Nunpa resides. His daughter was one of the first to climb the property fence in defense of the burial grounds the bulldozers. “We were proud to participate in those actions,” he said.

“I’m not here for spiritual reasons,” said Unpa Nunpa, who has resided at the camp for two moon cycles — the easiest way to keep track of time when days blur into weeks, he said. In spite of an incurable liver disease, for which he stopped taking his medication months ago, Unpa Nunpa said he is committed to the cause. “I’m here to defend Lakota treaty rights and to protect our water. This is my home, now,” he said.

“For 48 years, I’ve lived under this system, and I’m not the only one,” he said. “This is a chance for us to express our feelings about living underneath this system.”

In fact, the protest has provided a platform for the hundreds of native tribes represented here to voice their dissatisfaction with the way they’ve been treated for centuries — from what they see as generations of broken land treaties that led to cycles of unending poverty, sub-standard schools, and the pervasive racism facing their communities.

“This is the fearless generation,” Unpa Nunpa said. “They’ve got schools that have abused them, cops that have abused them, juvenile-justice systems that have abused them. They’ve endured domestic violence in their homes directed at them, they’ve endured substance abuse in their homes —particularly alcoholism — they’ve been bullied by their peers. They’ve gotten their asses kicked their whole life.”

He added, “So now we have a generation — and there’s hundreds of them just here in this camp — who are fearless and aren’t afraid to get their ass kicked. In fact, they want to kick some ass, now.”

Standing Rock has drawn tribes “who have had historical differences for a thousand years,” said Benalex Dupris, a professional comedian and Lakota native. “We’re all in the same camp together and we’re playing chess and we’re making jokes and we’re paddling on canoes from Alaska in the Missouri River.”

“This is the most significant gathering of native people in modern history and even if you’re just here to take a picture of yourself and say that I was there, it’s a documentation,” he said.

At the top of the hill that overlooked the main camp, a woman took a photo of her young daughter standing against the edge of the scene.

Below, the muted echo of ax blows could be heard. The drumbeat pulsed on, a horsed whinnied. Everything smelled like fire.