On Dec. 29, 1890, United States cavalry, in the last battle of the American Indian wars, massacred as many as 350 Lakota Sioux at Wounded Knee in South Dakota. Three generations later, Carter Camp, a 32-year-old Indian militant, retaliated.

On the night of Feb. 27, 1973, he led the first wave of armed, self-styled warriors in an operation to seize Wounded Knee, which had become a town on the Pine Ridge Indian Reservation. The invaders, carrying a list of grievances against the federal government, seized the trading post, cut the telephone lines, ran the Bureau of Indian Affairs police out of town and took 11 hostages.

"We were pretty sure that we were going to have to give up our lives," Mr. Camp said in an interview for the PBS program "American Experience" in 2009.

A caravan of 200 cars carrying Indians and their supporters followed, beginning a 71-day, gunshot-punctuated standoff that some applauded as a show of new assertiveness by long-downtrodden Indians and that others deplored as criminal.

By the time it was over, two Indians had been shot to death and a federal marshal was paralyzed. He later died. Mr. Camp was convicted of abducting, confining and beating four postal inspectors during the siege and served three years in prison.

He went on to spend decades fighting for Indian rights and died at 72 on Dec. 27 in White Eagle, Okla., the headquarters of the Ponca tribe, of which he was a member. The cause was kidney and liver cancer, his brother Craig said.

Carter Camp's dream was to regain the vast lands his people had lost through unfair and broken treaties. But he started by aiming his sights lower, leading a campaign in 1970 to change the way federal money for Indian education was allocated on the Ponca reservation. He became state leader of the American Indian Movement, or AIM, which was organized in 1968 in Minneapolis as a defender of American Indian sovereignty. In 1972, he helped lead an AIM caravan from the West Coast to Washington, where "red power" advocates occupied the Bureau of Indian Affairs building.

During the Wounded Knee occupation the next year, alongside the AIM leaders Dennis Banks and Russell C. Means, Mr. Camp was the spokesman who presented the group's demands to the government, among them that the government honor 371 broken treaties and that it end what the group called corrupt tribal governments. Mr. Camp rejected an offer of leniency if the protesters left immediately.

"We decided that the Indian people were more important to us than jail terms," he was quoted as saying in "The Road to Wounded Knee" (1974), by Robert Burnette and John Koster.

When the Indians finally did end their occupation, Mr. Camp was one of the leaders who signed the agreement. Mr. Banks did not.

In August 1973, Mr. Camp was elected chairman of AIM but within weeks was ejected from the organization after being accused of shooting another AIM leader, Clyde Bellecourt, in the stomach. News accounts and histories say Mr. Camp was angry that Mr. Bellecourt had accused him of being a paid informer for the F.B.I. Charges were dropped after Mr. Bellecourt and a witness refused to testify.

The episode precipitated swirls of speculation. In his 1983 book, "In the Spirit of Crazy Horse," Peter Matthiessen said Mr. Camp had called Mr. Bellecourt a coward because he refused to carry a gun. Others suggested that the F.B.I. had planted the rumor that Mr. Camp was an informer to damage AIM's credibility.

Bruce E. Johansen, the author of "Encyclopedia of the American Indian Movement" (2013), wrote that Mr. Bellecourt had tried to salvage Mr. Camp's reputation but that Mr. Means had insisted he be expelled.

Carter Augustus Camp was born in Pawnee, Okla., on Aug. 18, 1941. He graduated from Haskell Institute, a high school for Indians in Lawrence, Kan. (It became Haskell Indian Nations University.) He then joined the Army and served in Western Europe. After his discharge, he worked in a factory in Los Angeles, serving as shop steward for the electrical workers' union.

Mr. Camp returned to Oklahoma to be close to his roots, literally. "We believe the soil and every plant contains the dust of our ancestors," he once said.

In recent years, Mr. Camp had fought against garbage companies' using Indian lands for disposal; a proposed pipeline to bring tar sands oil from Canada; and a bar catering to motorcyclists near his reservation. He protested a re-enactment of the Lewis and Clark expedition, calling it a remembrance of the extermination of his people.

In addition to his brother, Mr. Camp is survived by another brother, Dwain; his wife, Linda; his sons Kenny, Jeremy, Victorio, Mazhonaposhe and Augustus; his sister, Casey Camp-Horinek; 24 grandchildren; and a great-granddaughter.

Mr. Camp helped organize annual sun dances conducted by Leonard Crow Dog, the spiritual leader of the Wounded Knee occupiers. Participants, who may not eat or drink, dance around a cottonwood tree from sunrise to sunset.