I think it was Herbert Khan, in the 1950s, who developed the concept of "scenario". His most popular and well known phrase in the 60s and 70s was "think the unthinkable." He was the first one to come up with the idea that the way to prevent nuclear war was to discuss in graphic detail what a nuclear war would be like. I assume he played a role in the development of the concept of "mutually assurred destruction." His ideas in the 50s helped shape how modern intelligence and planning is done in both government and business. Most modern intelligence agencies, even freelance ones, continue to generate scenarios that spell out both optimistic possibilities, but also explore the unthinkable. Art Kleiner has a reasonably concise history of all of this in his book The Age Of Heretics, which is about alternative ideas in the business world before 1980, before corporations started running commercials that say things like "It's a revolution! Be innovative!"