What term refers to the protection of US sovereignty, territory, domestic population, and critical defense infrastructure against external threats?

The term that refers to the protection of US sovereignty, territory, domestic population, and critical defense infrastructure against external threats is Homeland Defense. This concept specifically focuses on the defense of the nation from immediate and external threats, which encompasses the military's role in protecting the homeland against any form of aggression or attack. It includes measures taken by federal, state, and local governments to safeguard the population and maintain the integrity of national borders and infrastructure.

Homeland Security, while also integral to national safety, primarily deals with managing risks to the nation from internal threats, such as terrorism or natural disasters. National Security encompasses a broader scope, including diplomatic and military strategies on a global scale, while Military Readiness pertains to the preparedness and capability of armed forces to respond effectively in times of conflict. Homeland Defense is distinct because it hones in on the military aspect of protecting the homeland directly from external adversaries.