Some years ago I picked up this nice summary image of agile planning over several time cycles. It came from a white paper at AgileConnection.com " entitled "Scaling Agile Processes: Five Levels of Planning
Fortunately, to give some credibility to his thesis, the author says right up front that agile methods don't scale to enterprise level without some changes! He is so right. Since 2014 when the paper was written, SAFe (Scaled Agile Framework) and other scaling methodologies have come along and acquired creds in the community
So, as agile has matured, acquired some common sense, and worked its way into mainstream project protocols, even large scale organizations, like DoD, have embraced some tenants of agile methods.
You can check out some of the references to DoD practises I've gathered from Glen Alleman and others. As well, read some background in the white paper I wrote "back in the beginning" about agile in the DoD.
Better yet, give a read to "Project Management the Agile Way: Making it work in the enterprise, 2nd Edition"
Read in the library at Square Peg Consulting about these books I've written
Buy them at any online book retailer!
Read my contribution to the Flashblog