National security refers to the public policy of maintaining the integrity and survival of the nation-state through the use of economic, military and political power and the exercise of diplomacy, in times of peace and war.

Measures taken to ensure national security include:

• using diplomacy to rally allies and isolate threats
• marshalling economic power to facilitate or compel cooperation
• maintaining effective armed forces
• implementing civil defense and emergency preparedness measures (including anti-terrorism legislation)
• ensuring the resilience and redundancy of critical infrastructure
• using intelligence services to detect and defeat or avoid threats and espionage, and to protect classified information
• curbing pollution to ensure edible food and clean water supply and to decrease the potential for abrupt climate change