YAMBIO, South Sudan — Simon Burete was weeding his peanut field a few weeks ago when he saw smoke coming from his house. He ran as fast as he could.

He and his wife, Angelina, had enjoyed years of peace, he farming the fields, she selling the produce in the market. They were poor but welded to each other. Just that morning, they had talked about walking into town to buy their first mobile phones.

But as Mr. Burete made it back to the house, out of breath, red dirt still stuck to his knees, he couldn’t believe his eyes. His wife was lying on the floor, burned to death in a rampage by government forces.

“I used to call her akara-ngba,” he said, which means in the Zande language “the last word on beauty.”