National security is a corporate term covering both national defense and foreign relations of the U.S. It refers to the protection of a nation from attack or other danger by holding adequate armed forces and guarding state secrets. The term national security encompasses within it economic security, monetary security, energy security, environmental security, military security, political security and security of energy and natural resources. Specifically, national security means a circumstance that exists as a result of a military or defense advantage over any foreign nation or group of nations, or a friendly foreign relations position, or a defense position capable of successfully protesting hostile or destructive action.
In Cole v. Young, 351 U.S. 536 (U.S. 1956), the court observed that “the term "national security" in the Summary Suspension Act (64 Stat 476), authorizing the heads of specified federal agencies to summarily dismiss federal employees upon a determination that dismissal is necessary or advisable in the interest of the "national security," is used in a definite and limited sense and relates only to those activities which are directly concerned with the nation's safety, as distinguished from the general welfare.”