What is the primary role of a National Guard?

Answer 1

This is a difficult answer and I will try to make as short as I can. The shortest answer is that the Guard's role has changed significantly since the Korean War and beginning of Vietnam. The Guard took the place of Colony Militias in the transition from the 13 Colonies to the United States and remained under the control of State Governors... and they still do. (Remember, there was both the Continental Army and State Militias fighting the British in the Revolutionary War which had their greatest successes when working together under unified command.) However, with the advent of the Vietnam War, it's unpopularity among young people subject to the 3 year military service draft and voluntary nature of the National Guard, State governors allowed their State Militias (The Guard) to supplement active duty military draftees for service in Vietnam. (It was this ability to mobilize volunteers from the Guard that lead to the success of the All-Volunteer military force we have today.) In the oath of all people in government service, the line states, "defend the Constitution of the United States against all enemies Foreign and Domestic"... it was the intent of the Guard to defend against these Domestic Enemies; analogous to the "Home Guard" in the United Kingdom. The National Guard has taken on peacetime roles in disaster relief/recovery operations and humanitarian operations abroad. The Guard receives all its support from both the National and State governments and its total numbers of participants are strictly adhered to.

Answer 2

To defend and assist the United States and it's local state.

Answer 3

To serve and protect and render aid to both the state and the U.S.