For the first time since the end of the Cold War, the specter of nuclear armageddon looms over the world, as the Pentagon announced yesterday that a group of hillbillies in central Tennessee has constructed a fully operational 50-megaton nuclear device. The hillbillies successfully completed their first test detonation Monday in the Tennessee desert. With this potential for destruction in the hands of people who have throughout history acted out violently for no better reason than family tradition, scientists in Helsinki, Finland, have moved the doomsday clock back up to one minute before midnight. Pentagon officials were tipped off to the backwoods people's potential to invoke mass destruction last week when an I.R.S. agent returned from the Smoky Mountains claiming that a group of hillbillies had threatened to 'nuke him up real good.' The bomb's existence and operational status were later confirmed by a team of scientists who, after finding the weapon in a hay thresher, were run out of hillbilly territory by a family armed with a shotgun and three dogs named 'Duke.' The scientists describe the bomb as a plutonium-lined copper kettle which could easily be imploded to critical mass by igniting the whiskey-drenched possum pelts hanging around its perimeter. 'It is primitive yet brilliant,' said Dr. John Hall, the Pentagon's chief investigator. Hall was not sure how they got the plutonium, but said that their handling of it, wearing no more protection than baggy overalls, likely resulted in mutations far beyond those that regularly occur as a result of inbreeding. Granny Vera, the matriarch of the hillbillies in question, released a statement to the media yesterday by yelling across Ol' Thunder Gorge to a group of reporters gathered on the opposite cliff. 'We ain't dealin' with y'all no more!' she said. 'Now that we got us this 'nuke-lar' thing, y'all best stay off our land lest we commence to incin'ratin' folks 'till Hell won't have 'em!' She also ordered 'rev'nooers' to stay away, and warned 'them prohibition folk' to stop searching for her Pappy's stills. Though all hillbillies have joined together in solidarity against 'city folk,' military analysts worry that if feuding among clans were to resume, one side might decide to use more than buckshot. Said U.S. Secretary of Defense William Perry, 'We can only pray that the hillbilly culture is advanced enough to understand the sophisticated theory of peace through nuclear deterrence.' At this point, the Defense Department believes that the hillbillies possess no means of moving the warhead outside their territory. However, if the hillbillies' bomb were detonated in the epicenter of their community, it would have catastrophic effects on the outside, civilized world. With this in mind, President Clinton says his main goal is to get the hillbillies to dismantle their bomb entirely. To that end, he plans to negotiate with the hillbillies, offering them tax cuts, greater freedom in liquor production and a revocation of all laws prohibiting incest. 