BURNS, Ore. — The protesters arrived in this old lumber town to support a 73-year-old rancher and his son who had been sentenced to prison for setting fires that spread to federal lands. It was billed as a peaceful demonstration, but after “Amazing Grace” was sung and hugs were exchanged, a small, armed contingent declared outside a supermarket that it was taking a stand and asked who wanted to join.

So began the latest armed flare-up in a decades-long struggle between federal officials and local landowners and ranchers over how to manage the Western range. The armed antigovernment group seized empty administrative buildings on a federal refuge for wildlife about 30 miles away through the snowy sagebrush, and by Sunday night, had hunkered down for what they vowed would be an indefinite standoff with the government.

“We will be here for as long as it takes,” said Ryan Payne, an Army veteran who characterized the group’s action as a liberation of public lands. “People have talked about returning land to the people for a long time. Finally, someone is making an effort in that direction.”