Dr. Freidel, who specializes in Maya archaeology and was not involved in the new study, said it clearly showed that ordinary people had been targeted in the city. “The burning of Witzna shows that total war existed,” he said.

But he noted that there had been other cases of extreme violence, including massive destruction in Tikal, during a period from 100-250.

Dr. Wahl, who has done work on the ancient Maya for about 20 years, said the new research was serendipitous . He had identified a lake in Guatemala near the Witzna site that looked like a good research target.

It was. In lakes, he said, the rate of sediment accumulation varies greatly, so that one centimeter (about four-tenths of an inch) of a drilled lake bed core could represent the passage of anywhere from a decade to several centuries. But in the lake near Witzna, sediment had been deposited so rapidly that a centimeter represented less than a decade, perhaps close to one year. That meant it was an extraordinarily detailed record that could be tied closely to dates and records.

In the cores he drilled, he found a layer of charcoal three centimeters thick (about 1.2 inches), with chunks of charcoal almost a half inch on a side. Another author on the paper, Lysanna Anderson, a specialist in evidence of ancient fires, studied the layer. They concluded that it indicated a massive fire and had been deposited very quickly — all at once it seemed, although some might have been from runoff a season after the burning.

In addition, other chemical indications of human activity dropped off rapidly right after the event, he said, indicating that the human population itself had suddenly decreased. The fire had happened, they judged, between 690 and 700.

The next piece of evidence came from Francisco Estrada-Belli, another author who is an archaeologist at Tulane University. He found widespread destruction of buildings while excavating Witzna.