It may collapse shelters and some fighting positions. Thermal radiation causes burns and starts fires. The bright flash at the time of the explosion can cause a temporary loss of vision or permanent eye damage if you look at the explosion, especially at night. Nuclear radiation can cause casualties and delay movements. It may last for days and cover large areas of terrain.
Initial radiation is emitted directly from the fireball in the first minute after the explosion.
It travels at the speed of light along straight lines and has high penetrating power. Residual radiation lingers after the first minute. It comes from the radioactive material originally in a nuclear weapon or from material, such as soil and equipment, made radioactive by the nuclear explosion. EMP is a massive surge of electrical power. It is created the instant a nuclear detonation occurs and is transmitted at the speed of light in all directions.