This paper examines an aspect of United States armed forces that has been under-studied in the discipline of political science over the past three decades: the National Guard. The Guards roles, responsibilities, and relationships with the states and the federal government have changed significantly since the end of the Vietnam War, from weekend warriors to an integral component of the national security enterprise. The paper begins by defining the Guard and its constitutional role in American national security, and then evaluates the state of the political science literature on the National Guard. It illustrates changes to the Guard using three recent cases: the War on Drugs, the War on Terror, and Hurricane Katrina. Finally, it explores potential implications of these cases and other recent events on the future role of the National Guard in American politics.