South Sudan Raid Shows Rivals" Escalating Clashes NAIROBI, Kenya - About one week ago, an enormous column of 8,000 armed youths was advancing through the bush in South Sudan, bent on revenge. United Nations aircraft had been steadily tracking its movements and relaying information back to the head office in Juba, South Sudan's capital. Several hundred peacekeepers and government soldiers were rushed into place, but the authorities knew they were far outnumbered, and so they told residents to flee. "This was a massive, overwhelming force," said Lise Grande, the United Nations humanitarian coordinator in South Sudan. When the 8,000 rowdy fighters stormed Friday into their destination, the eastern Pibor area, they unleashed a spasm of destruction and violence on a rival ethnic group, burning down huts, looting stores and mercilessly hunting down women and children, witnesses said. They rampaged for several more days, and the young fighters were even so bold as to trade shots with the South Sudanese Army. But by Wednesday afternoon, the column of fighters seemed to be retreating, heading home with tens of thousands of stolen cows. And though the precise number of deaths is still unknown, a number of bodies have already been discovered, and Ms. Grande said the death toll would probably be "in the tens, if not the hundreds." South Sudan, the world's newest country, was born last July in ceremonies pulsating with pride and jubilation. Now, it seems to be exploding in violence. More than 1,000 people have been killed in the past several months in clashes between rival ethnic groups, often over cattle. Tensions between the neighboring Lou Nuer ethnic group and the smaller Murle have been percolating for months, if not years. Both prize cattle and have been viciously raiding each other's herds. This has escalated into full-fledged fighting between Murle and Lou Nuer youths, who are typically armed with automatic weapons. A few generations ago, such fighting was done with spears. The Murle killed more than 600 Lou Nuer last summer and abducted scores of women and children, which led to reprisals and then counter-reprisals. South Sudanese religious leaders tried to broker a truce in the fall, but the talks broke down over mistrust. In December, the Lou Nuer began to assemble its youths for a revenge raid. A force of 8,000 marched toward Pibor, razing the Murle village of Likwangoli along the way. South Sudan's vice president, Riek Machar, who is a member of the greater Nuer ethnic group, visited the massed fighters near Pibor last week and begged them to turn back. He was rebuffed as well. And so on Friday, around 1 p.m., the column of Lou Nuer fighters burst into the Pibor area, though most of the residents had heeded the warnings and fled. The Lou Nuer then waded into the bush around Pibor town, attacking civilians. When some fighters tried to cross a river and enter Pibor town, government forces fired at them, and the United Nations even mobilized armored personnel carriers, which might have been what caused the Lou Nuer to turn back eventually. Several Murle leaders are now expressing frustration over the lack of protection. "I've heard reports of pregnant women getting sliced up and their babies killed," said John Atiel, a Presbyterian pastor and a Murle, who spoke by telephone from Juba. He said that government forces had been unable - or unwilling - to safeguard civilians and that 150 people had been killed, maybe more. Calls to South Sudanese government officials went unanswered on Wednesday. Ms. Grande said that the United Nations had protected the town of Pibor as best as it could with its limited resources in South Sudan, where there are far fewer peacekeepers than in Darfur, the long-troubled but now relatively quiet area of western Sudan. She said the death toll could have been much higher had the United Nations not been closely following the movements of the Lou Nuer fighters. "It's not that the U.N. was panicking and saying, "Run for your lives," " she added. A key piece of protection is early warning and telling people to get out of the way, and that's exactly what we did. As many as 50,000 villagers are now displaced, living in the rugged South Sudanese bush with little food or water. "The humanitarian situation is grim," Ms. Grande said. Meanwhile, the aid organization Doctors Without Borders has lost contact with more than 100 of its local staff members, who scattered along with the local people into the bush. "We know roughly where they are," said Robin Meldrum, a spokesman for the organization. But we're still worried. We don't know if they're safe or not.