Take your pick, major war in the middle east involving Israel and thus pulling in the US and Russia, our economy and the fact it could fail at any time if China demanded repayment of its debt, civil unrest in this country of which there has been more of lately, if widespread could lead to martial law. Iran and North Korea and their ambitions, another terrorist attack on our soil which would lead to further draconian measures, an episdemic, I do not know but I do see the stage set for a number of possibilities. This is not including natural disasters and manmade ones as well. Those could cause widespread disruptions in food supply and water and many would not know how to cope without a grocery store or tap water.