http://www.newsweek.com/sun-nuclear-cold-war-1967-repeated-possible-solar-flare-1702239

In May 1967, a solar storm brought the world to the brink of what could have been a nuclear war. With the sun now entering a period of increased activity as part of its 11-year solar cycle, experts have discussed whether or not we should be wary of a second such incident.

The world was in the grips of the Cold War in 1967 when the sun belched out one of the largest solar storms ever observed at the time, releasing a colossal radio burst that interfered with communication services here on Earth.