Handling Domestic Threats: What's the Military Branch for That?

Not the usual type of question, but does anyone know which branch of the military typically handles domestic threats? I'm writing an essay on security policies, and this information would be quite useful.

Domestic threats are handled by multiple entities within the U.S. government, depending on the nature and scale of the threat. To understand this, it's important to note that the military and domestic law enforcement have consistently defined roles per the Posse Comitatus Act, which limits the military's ability to intervene in civilian affairs.

Generally speaking, the law enforcement agencies like the Federal Bureau of Investigation (FBI), U.S. Marshals Service, and local/state police departments handle domestic threats, particularly those that relate to crime or violent acts.

On the military front, the National Guard can be involved in handling domestic situations, but it's typically on a support or assistance level. This usually falls under the domain of what's called "Homeland Defense," and occur in situations like natural disasters, disease outbreaks, civil disturbances, or counter-terrorism missions. The National Guard, as a part of the state and federal military force, may be called upon by a state governor or, in rarer circumstances, the President for these situations.

On a larger, nationwide level, the Department of Homeland Security is the primary federal agency responsible for securing the nation from the many threats we face, such as terrorism, cybersecurity threats etc.

In writing your essay, it would be beneficial to address the system of checks and balances in place with laws such as the Posse Comitatus Act that are meant to ensure the military's power is not misused domestically.