Most people in India and in Pakistan (and in the U.S.) probably do not know that as many as 9 out of 10 people -- or more -- who die from a nuclear blast, do not die in the explosion itself. Most people probably think that if they die from a nuclear blast, they will simply see a flash and get quickly cooked.
Those within approximately a six square mile area (for a 1 megaton blast) will indeed be close enough to "ground zero" to be killed by the gamma rays emitting from the blast itself. Ghostly shadows of these people will be formed on any concrete or stone that lies behind them, and they will be no more. They literally won't know what hit them, since they will be vaporized before the electrical signals from their sense organs can reach their brains.
Outside the circle where people will be instantly vaporized from the initial gamma radiation blast, the light from the explosion (which is many times hotter than the sun) is so bright that it will immediately and permanently blind every living thing, including farm animals (including cows, sacred or otherwise), pets, birds while in flight and not to mention peasants, Maharajah's, and Government officials -- and soldiers, of course. Whether their eyes are opened or closed.
This will happen for perhaps 10 miles around in every direction (for a 1 megaton bomb) -- further for those who happen to be looking towards the blast at the moment of detonation. Even from fifty miles away, a 1 megaton blast will be many times brighter than the noonday sun. Those looking directly at the blast will have a large spot permanently burned into their retinas, where the light receptor cells will have been destroyed. The huge bright cloud being nearly instantly formed in front of them (made in part from those closer to the blast, who have already "become death"), will be the last clear image these people will see.
Most people who will die from the nuclear explosion will not die in the initial gamma ray burst, nor in the multi-spectral heat blast (mostly X-ray and ultraviolet wavelengths) which will come about a tenth of a second after the gamma burst. Nor will the pressure wave which follows over the next few seconds do most of them in, though it will cause bleeding from every orifice. Nor even will most people be killed by the momentary high winds which accompany the pressure wave. These winds will reach velocities of hundreds of miles an hour near the epicenter of the blast, and will reach velocities of 70 miles per hour as far as 6 miles from the blast (for a 1 megaton bomb). The high winds and flying debris will cause shrapnel-type wounds and blunt-trauma injuries.
Together, the pressure wave and the accompanying winds will do in quite a few, and damage most of the rest of the people (and animals, and structures) in a huge circle -- perhaps hundreds of square miles in area.
A 1 megaton nuclear bomb creates a firestorm that can cover 100 square miles. A 20 megaton blast's firestorm can cover nearly 2500 square miles. Hiroshima and Nagasaki were small cities, and by today's standards the bombs dropped on them were small bombs.
A significant percentage, probably most, of the people who die from a nuclear attack will die much later, from the widespread release of radioactive material into the environment. These deaths will occur all over the world, for centuries to come. Scattered deaths, and pockets of higher mortality rates, will continue from cancer, leukemia, and other health effects, especially genetic damage to succeeding generations.
Some deaths will occur hundreds and even thousands of miles away, because low levels of ionizing radiation are capable of causing the full spectrum of health effects, albeit at a lower rate within the population. Not to mention the radioactive runoff from the rivers and streams that flow through the blast area and the area under the radioactive mushroom cloud's drift. It may carry its deadly cargo for thousands of miles, raining a fallout of death only on some cities, and not on others. It will land upon nations which had not been involved in any way in India's dispute with Pakistan. These nations will be mighty hurt and mighty upset.
Finally, an atmospheric blast of a nuclear "device" creates an EMP (Electro-Magnetic Pulse) which can be as large as Pakistan or even India -- perhaps even larger than India and Pakistan together. The higher the altitude of the blast, the bigger the circle of damage will be from the EMP. This is a very serious concern for those of us in the high-tech industries, such as myself.
