For the record 'radioactive fallout' and 'EMP' affects are overrated and 'scares' about atomic devices mostly because we don't have everyday contact with atomic devices or their effects. Hence we 'exaggerate the threat' knowing that there is one...it's like how a legand is born from a true event.
The amount of fallout from an atomic varies greatly on if it is a fusion or fission primary detonation (fusion H-bombs use a small fission charge to ignite the fusion reaction, and so are still a bit 'dirty', even though the fusion reaction is for the most part clean), and if the bomb was an airburst or ground burst.
An air burst would be used against a large unsheiled target, like a city to create a shockwave through the atmosphere that compresses allong the ground front to deal preasure damage to structures.
Supprisingly the overrpressure is fairly low from this, and so long as your not stood out in the open within a couple of hundred metres of the epicentre you will come through the blast completly unscratched (apart from being very shocked). Unfortunatly 'not being out in the open', generally means being inside a building...the very object an airburst detonation is designed to destroy. Thus collasping rubble and flash fires started by flamable material caught in the heat radiation burst are your dangers.
Because the atomic reaction has very little contact with physical material fallout will be low.
Therefore damage to cities isn't 'total wipeout' to the population with a nuclear bomb, it's going to destroy free standing infrastructure but leave many people alive.
Ironically, the fact that in a nuclear war so many people would be left alive, but without the 'modern infrastructure' they are accustomed to, would be the major killer. Lack of fresh water, food, order and above all infomation would be the problems in the immidate aftermath. Not radiation or high technology not working...hell you've not got any power lines running into your city anymore (free standing structures your know)/the powerplant was within the shockwave radius.
Even more ironically, today even with the threat of full blown nuclear war on the wane, we are even more vunerable than we were 30 years ago. This is because our 'dynamic generation' 20-35 year olds, have grown up completly in a digital world in the west, and have very little concept of self survival or practical knowledge.
So when is fallout an issue? When you have a ground burst type weapon. In a ground burst the weapon is detonated close to, or on the ground, to create 'ground shock', essentially a mini earthquake designed to damage hardened structures. For instance an enemy missile silo.
Because the atomic reaction occurs close to the ground a greater amount of material comes within 'contact range', and so can be irradiated by gamma/x-rays produced in the photon burst.
Much of this material will be ground dust, and in the wake of the detonation the superheated air will rise in the atmosphere creating a rising cyclone, this breeze will draw dust kicked up in the intiall shockwave and drag it up into the lower-mid troposphere, where it may be carried by the prevailing winds and be dropped far from the initial source.
This is fallout, and while some fallout will be creating with an airburst it is a fraction of that of a ground burst. Since ground burst targets will be of a hardened millitary nature and not cities, there would be far less radioactive fallout than is portrayed in popular culture...if you live near a missile base though...sorry hard luck!
Even then radioactive fallout is not particularly dangerous if you recognise how to deal with it.
After many tests during the 50s of nuclear detonations dit was noted that the rapid movement of warm moist air from near the earth into the upper troposphere causes rainclouds to form, these rain clouds will create rain, and the rain dropplets would gather fallout from the air and concentrate it in the rainwater.
In the aftermath of a detonation services like mains water may be damaged, and that rain might appear as a god send to drink from or to collect to wash somebodies flash burns with.
However now that I've told you what that rain water contains you can see why this is particularly dangerous since you are taking a concentrated form of fallout an putting it either in contact with your skin (washing) or drinking it (ingesting radioactive material). For the record, radiation in this context is generally going to be charged ions (ionising radiation) when electrons were scattered out of the atomic shells of the atoms that make up the fallout matter. As such they will act a lot like alpha particles and so for the most part will be almost harmless unless ingested.
Most of these particles will disappate in the natural enviroment within a short time period (although the trace effects will exsit for decades).
Unfortunatly the people of Hiroshima and Nagisaki never knew any of this, and it might be estimated that a 3rd of all deaths were a result of exposure to the 'black rain' that fell after the detonations. While these early bombs weren't ground bursts, they would be nothing like the carefully calculated airbursts that might be seen in a 'cold war gone hot' in the 1980s.
Simply not drinking open water/eatting uncovered food and wearing body covering clothes in the hours and days just after a ground burst would save you from any radiation damage (within reason). If it was an airburst, you might not even need to take the procaution of body covering clothes. Although the point on food still stands since even a small amount of ingested radioactive matter is dangerous because it will at the bare minimum stay in your digestive tract for 8hrs or so, whereas material on your skin might get brushed off after only 10mins.
Because many people would be left alive within a couple of days law, order and civility might begin to crumble on the outskirts of crumbled cities, since the people who are left will not themselves have a clue about how to get food other than to raid it from supermarkets, or the 'authorities' who might be trying to deal with the situation.
People with weapons will be certain to use them. For the united state this is actually a major problem, since the avalibility of firearms in the state is much greater than Europe, Russia or Asia. Thus very quickly you'll resort to the law of the wild west, except with many more people fighting over much scarer resources.
For the united states the trouble in the weeks and months after a nuclear war might be simply not getting caught in the crossfire between armed gangs. 'Survivalists' in particular who have come up with 'bug-out plans', which is a big thing again in the US, will quickly take a dispropotionate share of undamaged supplies.
In the long run this means that these 'survivalists' are the most likely ones to pull through, and these will be precisely the anti-social, 'care only for me' types, which will make recovery and rebuilding more difficult. This would mean that for populaces with a high avalibility of weapons will more likely take longer to recover than nations which don't.
Britian in many respects could expect a fairly rapid return to 'normality' since its island nature will allow for boats to take the place of wrecked infrastructure. Refugees won't be able to flood in from other parts of europe, and the lack of police and civilian firearms place a much greater proportion of people as equals.
However a big part of 'picking up the pieces' would depend on the relative plans of nations. Some aspects of these are archived, but others are still classified.
Speaking from a general sense, the smart move for a government planning for widespread destruction of urban centres is not to focus on the urban centers, other than to halt the immidate damages caused by fires and loss of order.
If the people of the cities can be kept from flooding into the countryside regions and 'pillageing' then 'authority' can insure that agricultural industry can be maintained since it will not have been the targets of the nuclear stikes (unless a sadistic nation was trying to commit genocide). If the agricultural industry can be maintained, food sources can be maintained, therefore within a fairly short amount of time rations will be able to be set up and redistributed to the city regions.
With food, there will be hope. With hope people will trust their 'authority' and such will be able to not fall into a semi-anarchic state.
However the 'authority' that believes that it should suffer 'acceptable losses' and not care for the hit urban centres will find the city dwellers doing anything for food since they can't make it themselves.
Simmilarly a government that cannot organise in the aftermath to convice urban populaces to stay where they are will have issues with the local agriculture broken in the best intensions.
Having said this, attempting to save all areas won't work, particularly if the population itself is hostile. Triage will need to be conducted, in the manner that govenments choose will also dictate recovery. Harsher methods might instil order, but they also may weaken legitermacy of the 'authority'.
Of course the methods needed will be step-in-step with the level of force the civilian populations themselves can weid. Coming back to the notion of the avalibility of weapons, this is where armed schism can take place with official authority, and self-determined authority. In such cases all planning will go out the window for these areas.
Luckly most people of knowledge will survive, because many people will survive. So reorganising and dealing with these situations will just be another part of the recoverly process, slowing it down in some regions, while others not troubled by 'self-determined men' will get down to making the best of the situation and clear up.
As can be seen with recent tsunami in Japan, with relative order maintained even widespread destruction across the country can be repaired within a matter of months.
Of course, not all of Japan was affected, as would be the case in a nuclear war, but it shows how maintained order aids the recovery process.
If we contrast the Japanese tsunami with the Boxing day quake in 2004, vast communities all along Indonesia, Bangladesh and India have still not recovered. This is down to essentially a lack of general reconstruction planning and inaccess to modern equipment for reconstruction. However even here if we compare relative recovery, people were able to pick themselves up and deal with their losses and economic output today is about the same as it would have been without the quake and tsunami here. This shows that even if hundreds of thousands of people die, there are still those left with the knowledge to rebuild.
In fact if we think about percentages, using the data from the atomic bombings during WWII, only about 20-25% of the cities populations were killed by the bombs themselves. Which is a far cry from 90% of the population!
As we have seen above by considering the implications of the aftermath it makes more sense to kill as fewer a number of people, while causing the most damage to infrastructure, thus making the post war 'picking up the pieces' we a harder endeavour for your foe than yourself.
This means that you get back up on your feet first and take the upperhand.
Anyhow I ramble on,
If anybody would like to know more about blast effects and specific nations plans I can source some relevant information if you desire...
