Directive 51
John Barnes
 The title is a reference to Directive 51, the Presidential Directive which claims power to execute procedures for continuity of the federal government in the event of a "catastrophic emergency". In the near future, a variety of groups with diverse aims, but an overlapping desire to end modern technological society (the "Big System") create a nanotech plague ("Daybreak") which both destroys petroleum-based fuels, rubber and plastics and eats away any metal conductors carrying electricity. An open question in the book is whether these groups, and their shared motivations, are coordinated by some conscious actor, or whether they are an emergent property / meme that attained a critical mass. The Daybreak plague strikes, and world governments are helpless to deal with it. Industrial civilization rapidly breaks down, and tens of millions die in the US alone (the global death toll measures in the billions). There is a presidential succession crisis. Just as society in the US seems to start stabilizing, preemplaced pure fusion weapons detonate, destroying Washington DC and Chicago. This is followed by additional pure fusion weapon strikes, which are determined to be weapons that are being created on the moon by nanotech replicators. A shadowy neofeudalist group (the "Castle movement") led by a reactionary billionaire may be inadvertent saviors of society ... or may have some deeper involvement in things.