"The citizen militia system of the United States has been plagued historically by a confused and often contradictory basic philosophy. On the one hand, the militias were, and are, seen as crucial military resources available to the individual states to be used as local constabularies to assist the civil authorities in situations calling for skills, organization and capabilities beyond the level of local police, fire and disaster relief agencies. On the other hand, the citizen militias have been seen, increasingly in the 20th century, as an essential reserve of trained personnel available for mobilization to active service with the regular Armed Forces of the nation."
State Guard Association of the United States: http://www.sgaus.org/
Military Review (September 1984)