The use of nuclear weapons is widely viewed as a clear breach of international humanitarian law due to the enormous levels of harm that it would cause. Even the detonation of a single weapon can kill many thousands, injure tens of millions and create untold suffering for billions more, with the young, old, pregnant women, those already sick or vulnerable, the injured and the disabled especially at risk.

When a nuclear bomb explodes, it creates intense fires that burn and pulverize everything within a wide area around the point of impact. The blast wave that accompanies a nuclear explosion is also very dangerous and can knock people over and cause damage to buildings and cars. A nuclear explosion can be heard for miles and will be accompanied by a loud, sustained boom that sounds like a gunshot or thunder clap.

Depending on the target, air bursts – used to destroy cities and buildings and hardened military targets such as underground missile silos – leave lethal levels of radiation behind that could poison the food supply for tens of kilometres and lead to widespread diseases from radioactive debris (see section 5). In addition, the long term effects of nuclear warfare on the climate and agricultural production will make it very difficult for any human being to survive in a ravaged and traumatised world (see section 6).

It has been suggested by some western game theorists that it is possible to use a small number of low-yield nuclear weapons to show resolve with the hope that this will make the other side back down and go back to the negotiating table (this is known as escalate to deescalate). However, many scientific studies and military simulations have shown that even the use of a few low-yield nuclear weapons will be a catastrophe with far-reaching impacts.