Historically, an army would have days, weeks, or even months to prepare for war. However, with the development of intercontinental missiles and nuclear weapons, the time for preparation was reduced to hours or even minutes. In light of these changes, it was necessary to develop a system that allowed for rapid mobilization and readiness. Learn more about the DEFCON system, and the history of its level changes, on this episode of Everything Everywhere Daily. Learn more about your ad choices. Visit megaphone.fm/adchoices