Backed by tanks and artillery, soldiers from Uganda sneaked across the border with South Sudan and opened fire on troops long considered to be allies, South Sudanese officials said on Wednesday. When the firefight was over, the bodies of eight men, some in army fatigues, one in bluejeans, were left crumpled and bleeding on the ground. It was not immediately clear what prompted the surprise attack in the border county of Kajo Keji in South Sudan, a country teetering on the edge of civil war. Uganda has long provided military support to the South Sudanese government. … More than 100 people were displaced by the fighting, Bishop Nicanor said. The firefight, which erupted on Monday, represented a rare clash between the longtime security partners at a time when the hard-won stability of oil-rich South Sudan is increasingly at risk. In March, after years of slow progress toward cohesion, the South Sudanese vice president was placed under house arrest in a political standoff. The same month a Ugandan official said the country had deployed troops to South Sudan’s capital, Juba, in support of the South Sudanese president. New York Times