BUNIA, Congo - For six days, two terrified United Nations military observers phoned their superiors - as many as four times a day - begging to be evacuated from their remote outpost in northeastern Congo. They were receiving death threats, they said. They were alone and unarmed in Mongbwalu, a former gold-mining town ruled by the cannibalistic Lendu tribal militias. A U.N. helicopter from the town of Bunia could have retrieved them in 35 minutes. But the United Nations, handcuffed by its own rules and bureaucracy, never sent a chopper. On May 18, 10 days after the two peacekeepers...