F-hour Definition - MilitaryDictionary.org
1.) Effective time of announcement by the Secretary of Defense to the Military Departments of a decision to mobilize Reserve units.
In the United States, military vocabulary is standardized by the Department of Defence. These terms are used by the United States Army, Navy, Air Force, and Marine Corps.
Department of Defence, Dictionary of Military and Associated Terms
This term is marked as active and was last updated in 2015
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