Unity of effort is an essential concept in emergency management to provide a rapid and coordinated response. The command relationships between active and National Guard forces conducting operations in domestic disaster response become an issue when both types of forces are operating in the same area and responding to different authorities. How authorities establish command relationships and form new organizations between these forces contributes to unity of effort during Defense Support to Civil Authorities operations. This study examines three command relationship models, applies an understanding of the organizations and structures of emergency management and the integration of state and federal military forces into emergency response operations within California. This thesis finds that the integration and a unified command and control of these forces are essential in providing the incident commander with unity of effort and the Dual-Hat command relationship provides the most effective model to ensuring unity of effort in emergency response operations between active and National Guard forces within California. This model provides the Unity of Command necessary to effectively coordinate and direct military operations, while providing the JTF commander the flexibility to use the appropriate capabilities and assets of both the active and National Guard.