Civil defense is an effort to defend civilian society from military attack. Like emergency operations, it has four basic tasks: mitigation, preparation, response, and recovery. In a civil defense context, these usually have different tasks.
Relatively small investments in recovery aids can speed up recovery by months or years, and thereby prevent millions of deaths by hunger, cold and disease. For example, a crucial need after a general nuclear attack would be diesel fuel to transport every other item for recovery. However, oil refineries are large, immobile, and probable targets. One proposal is to preposition truck-mounted diesel refineries near oil fields and bulk storage depots. Other critical infrastructure needs would include road and bridge repair, communications, electric power, food production and potable water.
During the Cold War, civil defense was seen largely as defending against and recovering from an attack involving nuclear weapons. After the end of the Cold War, the focus moved from defense against nuclear war to defense against a terrorist attack possibly involving chemical or biological weapons. After the September 11, 2001 attacks, the concept of civil defense has been revisited under the umbrella term of homeland defense.
Mitigation is the process of actively preventing the war or the release of nuclear weapons. It includes policy analysis, diplomacy, political measures, and more military responses such as a National Missile Defense and air defense artillery. In the case of counter-terrorism, mitigation would include intelligence gathering and direct action against terrorist groups. Mitigation may also be reflected in long-term planning such as the design of the interstate highway system and the placement of military bases further away from populated areas.
Preparation consists of building shelters, and prepositioning information, supplies and emergency infrastructure. For example, most larger cities in the U.S. now have emergency operations centers that can perform civil defense coordination. Other measures would include continuous government inventories of grain silos and fuel storage systems, and the dispersal of truck-transportable bridges, water purification, mobile refineries and other aids to speed civil recovery.
On an individual scale, one means of preparation for exposure to nuclear fallout is obtain potassium iodide (KI) tablets as a safety measure to protect the human thyroid gland from the uptake of dangerous radioactive iodine.
Response consists first of warning civilians so they can enter shelters and protect assets.
Staffing a response is always problematic in a civil defense emergency. After an attack, conventional full-time emergency services are dramatically overloaded, with conventional fire fighting response times often exceeding several days. Some capability is maintained by local and state agencies, and an emergency reserve is provided by specialized military units, especially civil affairs and combat engineers.
However, the traditional response to massed attack on civilian population centers is to maintain a mass-trained force of amateur emergency workers. Studies in World War II showed that lightly trained (40 hours or less) civilians in organized teams can perform up to 95% of emergency activities when trained, liased and supported by local government. In this plan, the populace rescues itself from most situations, and provides information to a central office to prioritize professional emergency services.
In the 1990s, this concept was revived by the Los Angeles, California Fire Department to cope with civil emergencies such as earthquakes. The program was widely adopted, providing standard terms for organization. In the U.S., this is now official federal policy, and it is implemented by community emergency response teams, under the Department of Homeland Defense, which certifies training programs by local governments, and registers "certified disaster service workers" who complete such training.
Recovery consists of rebuilding damaged infrastructure, buildings and production. The recovery phase is the longest and ultimately most expensive phase. Once the immediate "crisis" has passed, cooperation fades away and recovery efforts are often politicized or seen as economic opportunities.
Preparation for recovery can be very helpful. If mitigating resources are dispersed before the attack, cascades of social failures can be prevented. For example, a crucial need after a general nuclear attack would be diesel fuel to transport every other item for recovery. One hedge against bridge damage in riverine cities is to subsidize a "tourist ferry" that performs scenic cruises on the river. When a bridge is down, the ferry takes up the load.
Some advocates believe that government should change building codes to require autonomous buildings in order to reduce civil societies' dependence on complex, fragile networks of social services.