This paper examines all aspects of homeland defense of the United States. First it provides a historical perspective on the Homeland Defense mission and identifies future threats. Each major threat area is then examined to determine what our response should be against that threat, to include identifying specific missions. Each mission is assessed for its compatibility with Active Duty Forces and with Reserve Component Forces using the criteria of trust of the American people, availability of personnel and equipment and the ability to adequately perform the mission. The similarities of the Active and Reserve capabilities along with their differences are compared to make an argument for the role each should play in providing a strong homeland defense for the United States of America. This paper finally recommends that the National Guard take the lead role in specific homeland defense missions, with follow on forces from the Reserve and Active Duty military services. The special relationship enjoyed with the civilian community by the reserve components should be used to leverage military support to civil authorities.