Nuclear warfare
CRP-2B, for instance, infamously predicted that 80% of Americans would survive a nuclear exchange with the Soviet Union, a figure that neglected nuclear war's impacts on healthcare infrastructure, the food supply, and the ecosystem and assumed that all major cities could be successfully evacuated within 3–5 days. A number of Cold War publications advocated preparations that could purportedly enable a large proportion of civilians to survive even a total nuclear war. Among the most famous of these is Nuclear War Survival Skills.
To avoid injury and death from a nuclear weapon's heat flash and blast effects, the two most far-ranging prompt effects of nuclear weapons, schoolchildren were taught to duck and cover by the early Cold War film of the same name. Such advice is once again being given in case of nuclear terrorist attacks.
Prussian blue, or "Radiogardase", is stockpiled in the US, along with potassium iodide and DPTA, as pharmaceuticals useful in treating internal exposure to harmful radioisotopes in fallout.
Publications on adapting to a changing diet and supplying nutritional food sources following a nuclear war, with particular focus on agricultural radioecology, include Nutrition in the postattack environment by the RAND corporation.
The British government developed a public alert system for use during a nuclear attack with the expectation of a four-minute warning before detonation. The United States expected a warning time of anywhere from half an hour (for land-based missiles) to less than three minutes (for submarine-based weapons). Many countries maintain plans for continuity of government following a nuclear attack or similar disasters. These range from a designated survivor, intended to ensure the survival of some form of government leadership, to the Soviet Dead Hand system, which allows for retaliation even if all Soviet leadership were destroyed. Nuclear submarines are given letters of last resort: orders on what action to take in the event that an enemy nuclear strike has destroyed the government.
A number of other countries around the world have taken significant efforts to maximize their survival prospects in the event of large calamities, both natural and manmade. For example, metro stations in Pyongyang, North Korea, were constructed 110 metres (360 ft) below ground, and were designed to serve as nuclear shelters in the event of war, with each station entrance built with thick steel blast doors. An example of privately funded fallout shelters is the Ark Two Shelter in Ontario, Canada, and autonomous shelters have been constructed with an emphasis on post-war networking and reconstruction.
In Switzerland, the majority of homes have an underground blast and fallout shelter. The country has an overcapacity of such shelters and can accommodate slightly more than the nation's population size.
While the nuclear fallout shelters described above are the ideal long-term protection methods against dangerous radiation exposure in the event of a nuclear catastrophe, it is also necessary to have mobile protection equipment for medical and security personnel to safely assist in containment, evacuation, and many other necessary public safety objectives which ensue as a result of nuclear detonation. There are many basic shielding strategies used to protect against the deposition of radioactive material from external radiation environments. Respirators that protect against internal deposition are used to prevent the inhalation and ingestion of radioactive material and dermal protective equipment which is used to protect against the deposition of material on external structures like skin, hair, and clothing. While these protection strategies do slightly reduce the exposure, they provide almost no protection from externally penetrating gamma radiation, which is the cause of acute radiation syndrome and can be extremely lethal in high dosages. Naturally, shielding the entire body from high-energy gamma radiation is optimal, but the required mass to provide adequate attenuation makes functional movement nearly impossible.
Recent scientific studies have shown the feasibility of partial body shielding as a viable protection strategy against externally penetrating gamma radiation. The concept is based in providing sufficient attenuation to only the most radio-sensitive organs and tissues in efforts to defer the onset of acute radiation syndrome, the most immediate threat to humans from high doses of gamma radiation. Acute radiation syndrome is a result of irreversible bone marrow damage from high-energy radiation exposure. Due to the regenerative property of hematopoietic stem cells found in bone marrow, it is only necessary to protect enough bone marrow to repopulate the exposed areas of the body with the shielded supply. Because 50% of the body's supply of bone marrow is stored in the pelvic region which is also in close proximity to other radio-sensitive organs in the abdomen, the lower torso is a logical choice as the primary target for protection.

In fiction: Nuclear warfare and weapons are staple elements of speculative fiction.

See also: 

References: 

Further reading: Louis Beres, Apocalypse: Nuclear Catastrophe in World Politics. The risks and consequences of nuclear war and nuclear terrorism. University of Chicago Press, Chicago, 1980. ISBN 9780226043609
Laura Grego and David Wright, "Broken Shield:  Missiles designed to destroy incoming nuclear warheads fail frequently in tests and could increase global risk of mass destruction", Scientific American, vol. 320, no. no. 6 (June 2019), pp. 62–67.  "Nuclear-armed missiles are a political problem that technology cannot solve....  Current U.S. missile defense plans are being driven largely by technology, politics and fear.  Missile defenses will not allow us to escape our vulnerability to nuclear weapons.  Instead large-scale developments will create barriers to taking real steps toward reducing nuclear risks—by blocking further cuts in nuclear arsenals and potentially spurring new deployments."  (p. 67.)
Jessica T. Mathews, "The New Nuclear Threat", The New York Review of Books, vol. LXVII, no. 13 (20 August 2020), pp. 19–21. "[P]owerful reasons to doubt that there could be a limited nuclear war [include] those that emerge from any study of history, a knowledge of how humans act under pressure, or experience of government." (p. 20.)
"Possibility of Nuclear War in Asia: An Indian Perspective", a project of United Service Institution of India, USI, Discusses the possibility of a nuclear war in Asia from the Indian point of view.
Thomas Powers, "The Nuclear Worrier" (review of Daniel Ellsberg, The Doomsday Machine:  Confessions of a Nuclear War Planner, New York, Bloomsbury, 2017, ISBN 9781608196708, 420 pp.), The New York Review of Books, vol. LXV, no. 1 (18 January 2018), pp. 13–15.
"Presidency in the Nuclear Age", conference and forum at the JFK Library, Boston, October 12, 2009. Four panels: "The Race to Build the Bomb and the Decision to Use It", "Cuban Missile Crisis and the First Nuclear Test Ban Treaty", "The Cold War and the Nuclear Arms Race", and "Nuclear Weapons, Terrorism, and the Presidency".
Tom Stevenson, "A Tiny Sun" (review of Fred Kaplan, The Bomb: Presidents, Generals, and the Secret History of Nuclear War, Simon and Schuster, 2021,  384 pp.; and Keir A. Lieber and Daryl G. Press, The Myth of the Nuclear Revolution: Power Politics in the Atomic Age, Cornell, 2020, 180 pp.), London Review of Books, vol. 44, no. 4 (24 February 2022), pp. 29–32. "Nuclear strategists systematically underestimate the chances of nuclear accident... [T]here have been too many close calls for accidental use to be discounted." (p. 32.)

External links: 
Fallout: After a Nuclear Attack – slideshow by Life magazine
The Effects of Nuclear War Archived 2016-08-28 at the Wayback Machine (1979) — handbook produced by the United States Office of Technology Assessment (hosted by the Federation of American Scientists)
Nuclear Attack Planning Base – 1990 (1987) — assessment of the effects of a major Soviet attack on the United States produced by the Federal Emergency Management Agency (hosted by the Federation of American Scientists)
Nuclear War Survival Skills (1979/1987) — handbook produced by Oak Ridge National Laboratory (use menu at left to navigate)
Ground Zero: A Javascript simulation of the effects of a nuclear explosion in a city
British RAF manual on the effects of nuclear explosions dated 1955
20 Mishaps That Might Have Started Accidental Nuclear War by Alan F. Philips, M.D.
Nuclear Files.org Archived 2013-03-29 at the Wayback Machine Interactive Timeline of the Nuclear Age
Annotated bibliography on nuclear warfare from the Alsos Digital Library for Nuclear Issues
DeVolpi, Alexander, Vladimir E. Minkov, Vadim A. Simonenko, and George S. Stanford. 2004. Nuclear Shadowboxing: Contemporary Threats from Cold War Weaponry, Vols. 1 and 2. Fidlar Doubleday.
Air Weapons for the Cold War Archived 2013-07-24 at the Wayback Machine An in depth history of American air weapons and nuclear bombs from the reference book American Combat Planes of the 20th Century by Ray Wagner
Nuclear Emergency and Radiation Resources
NUKEMAP3D – a 3D nuclear weapons effects simulator powered by Google Maps.
Return of Hitler, World War III