The Pibor area is one of the most rugged and isolated parts of South Sudan, surrounded by thick forests and swamps. With thousands of fighters still roaming around and many roads inaccessible, United Nations officials said they would not know the full extent of the violence for several more days.

Image Thousands of armed fighters attacked the town of Pibor. Credit... The New York Times

South Sudan’s military spokesman, Col. Philip Aguer, said, “I’m sure many people died.” But the army, like the United Nations, was waiting for more details, he said.

“I feel bad,” Colonel Aguer said. Referring to the South Sudanese Army, he continued: “It is regrettable that the SPLA couldn’t stop this. This region is in conflict. This is not the first incident of this kind, and it will not be the last.”

The cattle-rustling tradition in this part of South Sudan goes back generations. Both the Murle and the Lou Nuer prize cows and often lionize the young warriors who steal them. Years ago, the warriors clashed with spears. Now, they use AK-47s.

Last year, the Lou Nuer attacked several Murle villages, stole cattle and killed hundreds. The Murle responded by attacking several Lou Nuer villages, stealing cattle and killing hundreds. The two groups often abduct women and children during these raids. Church elders tried to intervene, but talks broke down in December. Then the Lou Nuer began amassing a huge force of heavily armed youths. Lou Nuer elders said it was time to wipe out the smaller Murle group, once and for all.

In late December, the column of Lou Nuer fighters began marching toward Pibor, burning huts along the way. The United Nations rushed 400 peacekeepers to Pibor, trying to defend the town alongside about 400 South Sudanese government troops.

But as Colonel Aguer said, “800 can’t stop 6,000.”

When asked why so few soldiers were defending Pibor when it was clear an enormous force of Lou Nuer fighters was headed that way, he replied, “It’s a long story.”