NDA
An area established on nonfederal lands located within the United States or its possessions or territories for the purpose of safeguarding classified defense information or protecting Department of Defense equipment and/or material.
Establishment of a national defense area temporarily places such nonfederal lands under the effective control of the DoD and results only from an emergency event. The senior DoD representative at the scene will define the boundary, mark it with a physical barrier, and post warning signs. The landowner's consent and cooperation will be obtained whenever possible; however, military necessity will dictate the final decision regarding location, shape, and size of the national defense area.
See the Introduction, Abbreviations and Pronunciation for further details.