Before Chuck Boers joined the U.S. Army, the Lipan Apache member was given his family's eagle feathers. The feathers had been carried by his great-great-great-grandfather on his rifle when he was an Apache scout.

They also were carried by relatives who fought in World War I, World War II, Korea and Vietnam. In 2004, Boers had the feathers with him during the Battle of Fallujah in Iraq. "I felt like I had my family with me to protect me," he said.

"The Warrior Tradition," a new film set to air on PBS, examines the complex history of Native Americans in the U.S. military since World War I and how their service transformed the lives for Native Americans from various tribes. Through interviews with veterans and using archival footage, the documentary probes the complicated relationship Native Americans had with military service and how they used it to press for civil rights.

The documentary exhibits the mixed feelings some Native Americans felt toward the U.S. military and how tribal members embraced those who served as "warriors."

"From just about the beginning of the United States itself, the government has fought various wars against Native nations. And that's the irony," Patty Loew, director of the Center for Native American and Indigenous Research at Northwestern University, said in the film.

But Native Americans, from tribes in Oklahoma to nations in Washington, joined the U.S. military to honor their "end of the treaty" that the U.S. government previously broke, Loew said.