According to Strauss and Howe , there are many potential threats that could feed a growing sense of public urgency as the Fourth Turning progresses , including a terrorist attack , a financial collapse , a major war , a crisis of nuclear proliferation , an environmental crisis , an energy shortage , or new civil wars . The generational cycle can not explain the role or timing of these individual threats . Nor can it account for the great events of history , like the bombing of Pearl Harbor , President Kennedy ’s assassination , or 9/11 . What the generational cycle can do , according to Strauss and Howe , is explain how society is likely to respond to these events in different eras . It is the response , not the initial event , which defines an era according to the theory . According to Strauss and Howe , the crisis period lasts for approximately 20 years
9/11
September 11 attacks
Strauss–Howe generational theory