That alone will bring any India/Pakistan conflict to a quick halt, while the fatalities and damage from economic collapse and social breakdown will far exceed the physical effects of several dozen relatively primitive nuclear weapons used on cities.
The media's failure to explain the certain collapse of both sides arises from (a) ignorance (which is largely the military's fault though the press should rely on other sources too), (b) political ideology and (c) superstition - anything in the movies and comic books must be true. The military has no such excuses. It has for generations been blind to the effects of its operations on its own side. This was repeatedly demonstrated in exercises, and even in Croatia during our intervention in Bosnia. Also see this writer's article in the February 1988 Journal of Civil Defense.
The driving factor in all recent crises between India and Pakistan has been the latter's support of terrorism in Kashmir for domestic Pakistani political reasons. Originally this was a vehicle for the Pakistani Army to take over the government (successfully so for its current President, ex-general Musharraf). The Pakistani Army's support for Islamic extremism served the same purpose, but then Islamic extremists merged with Pakistan's Inter-Service Intelligence (ISI) and formed an alliance with Osama bin Laden's Al Qaeda terrorists.
Musharraf was forced to change sides last year, under threat of Pakistan's extinction at American hands, but has not succeeded in taming the ISI. And the ISI's Islamic extremists are fomenting terrorism in India's portion of Kashmir as a means of gaining control of Pakistan for themselves. A war with India would help them do that, especially a conventional one which Pakistan loses.
The United States would find such a war a potent distraction from its buildup to the conquest of Iraq, and a major impediment to elimination of Al Qaeda remnants in Afghanistan and Pakistani bases. Islamic terrorism in Kashmir really is another front in America's war on terror. The US government denies this but it is true, and it is true because the ISI's terrorists are cooperating with Al Qaeda against us, not because of anything we do or don't do.
So it is likely that the United States will put great pressure on India not to attack Pakistan until we've conquered Iraq. India is not dependent on the US for anything so our major influence comes from incentives, not punitive disincentives. There is one coin which can truly buy India's short-term inaction - promised American support for India's later conquest of Pakistan. Such conquest would permanently protect India from Pakistan's growing nuclear arsenal, and from Pakistani state-supported terrorism.
But such conquest gets us back to nuclear weapon effects. Those are greatly exaggerated. Nuclear weapons used in the mass numbers of a US/Soviet exchange can destroy civilized life in most countries, but India and Pakistan have less than a hundred each, and small, primitive ones at that. American nuclear attack planners in the Cold War used a rule of thumb that effective destruction of a city required covering all important areas with a five pound per square inch overpressure from the blast wave, which would also be the effective burn-out area. One to several dozen nuclear airbursts were deemed required for destruction of large cities, which given reliability, serviceability and targeting problems meant targeting a single large city with 50-100 warheads.
And those were much larger than the primitive weapons possessed by India and Pakistan. Those tend to be in the 30 kiloton yield range, which produces a 5 psi overpressure blast wave at 1.33 miles from epicenter (2.16 km). All of Pakistan's nuclear weapons would be required to destroy a single large Indian city, and vice versa, to the degree assumed in movies and thriller novels. With no short-term fallout as airbursts don't produce any.
But almost all of India and Pakistan's nuclear weapons would be used against the other side's nuclear weapons (called a "counterforce" strike), and those would produce some, but not much, short-term fallout. Only a few nuclear strikes against cities, and probably just one against even a military target, would be required to cause mass panic and the collapse of both sides. That is easily within their capabilities, and would produce at least a million, possibly several million deaths from chaos, disease and starvation. -- Thomas M. Holsinger
Nuclear War Between India And Pakistan?- The current "crisis" between India and Pakistan over Kashmir is unlikely to erupt into a nuclear exchange, for the usual reasons, and, if it ever does, is unlikely to have the results commonly reported. The most likely result of use of even one nuclear weapon by either side on the other will be the immediate economic collapse of both countries as most everyone in their cities runs away fast.