From the Abstract: "As doctrine continues to evolve towards multi-domain battle, the homeland is under increasing risk. In the multi-domain extended battlefield, US reliance on the defense industrial base and strategic lines of communication present adversaries with unique opportunities. At the same time, access to domestic critical infrastructure and key resources in the cyber domain could put the homeland in play in the next war. Efforts to protect the nation's infrastructure in the cyber domain currently remain largely focused on cyber-defense. What if a threat actor successfully penetrated cyber-defenses and impacted critical infrastructure? What would the defense response look like if this attack came during a major combat operation? Would such an attack be defense support to civil authorities (DSCA) or homeland defense (HD), and does it matter? This thesis explores these questions by analyzing the current DSCA doctrine and comparing it to current cyber threats."