What term is used to define protection against attack?

The term that defines protection against attack is "Defense." This term specifically refers to actions or measures that are taken to protect a person, organization, or territory from threats or aggressions. In military contexts, defense encompasses strategies, tactics, and systems put in place to deter or respond to attacks, thus providing a clear framework for safeguarding individuals or assets from external harm.

While "Security," "Protection," and "Safeguard" all relate to the concept of keeping individuals or entities safe from threats, they carry slightly different connotations. "Security" often encompasses broader measures that include surveillance and risk management, "Protection" refers more generally to the act of keeping someone safe, and "Safeguard" suggests a protective measure that can be put in place to prevent harm. However, when specifically addressing the action taken in response to an attack or the measures employed to thwart aggression, "Defense" is the most precise term.