Washington, Dead City Series

An ancient fundamentalist organization executes several attacks simultaneously across the globe. A deadly viral compound is unleashed in the Pentagon, and the airborne virus turns the building's population into zombies. A Secret Service agent, coerced by the terrorists to assassinate several heads of state, sends the world into chaos. 

Six years ago, the president made the difficult decision to abandon Washington to the undead...Now, a new presidential election revives the hopes of the nation as one candidate promises to retrieve the Declaration of Independence and Constitution from behind The Wall. Retired CIA operative Asher Hawke, AKA the Kestrel, agrees to lead a team to recover the national treasures. But when they insert behind The Wall, they discover that organized crime families have been stealing priceless artwork and cash as well as disposing of bodies behind The Wall.

It takes political intrigue - and plenty of tanks - to defeat zombies. Escaped zombies from behind the wall have swept across the northeast, their path marked by havoc and death. Into this nightmare world are thrust several unlikely heroes. A full-time national guard soldier leads his company of tanks on a harrowing journey towards the Appalachian Defensive Line. A small group of refugees fight for their own survival and end up facing demons of a different sort.