The Guiness Book of World Records had an entry in their bombs and explosions section about a doomsday device that may have been built. This info was back in the 1970's and was apparently deleted from later editions. The weapon and effects of use described is similar to machines now discussed. One wonders where the Guiness folk got their info. Both types of weapons are essentially radiation-enhanced devices. Such devices were planned back in the 1950's (called cobalt bombs) by both the U.S. and Russia for use against China. The intention was to kill off the numerically larger Chinese Army but spare industry and resources (obviously the civilian population would not survive). It is also my understanding from other sources that both the Russians and U.S. have at least two types of verification systems (including both satellite detection and radar) that reduces the chance of an accidental war. A rogue nuclear explosion, such as terrorist attack, would not itself start a war.