Here is a simple descriptive answer to the OP's question from this source - A nuclear attack could cause substantial fatalities, injuries, and infrastructure damage from the heat and blast of the explosion, and significant radiological consequences from both the initial nuclear radiation and the radioactive fallout that settles after the initial event. An electromagnetic pulse from the explosion could also disrupt telecommunications and power distribution. The energy released by a nuclear explosion is distributed roughly as 50% shockwave; 35% heat; 5% initial nuclear radiation; and 10% fallout radiation. This distribution varies depending on the design of the weapon and the altitude of the explosion. In short, nothing would survive.