The missiles are launched and all the big cities in the world are engulfed in nuclear fireballs. A nuclear cloud spreads around the globe, the dark settles in, and a nuclear winter spreads across the northern hemisphere. How long until civilisation rebuilds?
THE RISE OF WARLORDS - OR NOT?
As survivors dug themselves out of fallout shelters and started competing for food and ammo, my guess is that some more thoughtful types would already be thinking about what lay ahead. My guess is that as well as grabbing all the food and water systems they could set up, some would be trying to find out if anyone was in charge. Was the President alive (or Prime Minister if we're talking about Australia and other southern nations, which might avoid a lot of the nuclear winter.) Was the State leadership intact? What about the local Mayor? Because most of us have seen Mad Max and the Book of Eli and know that after the disaster, one immediately needs to set up the rule of law or the despots take over. Once the road warriors take over, many good things can be lost from sheer brutish stupidity.
I think sheer self-interest would have many of us pushing to vote for a local town mayor and body of laws. We know the rule of law is a fragile thing, and the horrors if we miss it.
(But even if some crazy warlord takes over – with their militias scaring everyone into submission - this can become a type of order. Even warlords want their food hot and beer cold, want power systems and some sort of order to keep the power on. Technical progress would be desirable, even if the political progress came through painful revolutions later on.)
DEMOCRACY
I would bet on Democracy making a quick comeback. We like the rule of law! Local citizens would vote on things, organise things, and get things done. Before the year was out I’d bet that even if the national government had completely collapsed in the nuclear holocaust, that local people would have set up their own local systems of democratic law. Local mayors would start to negotiate trade deals with other village mayors. Within a few years, enough mayors might have formed together to re-institute State laws and have a State police force and army to protect them from warlords!
INDUSTRIALISING AGAIN
Meanwhile there are scavenging and technical guilds as well as farming guilds forming. They're putting back into their local environment, their farms, their soil, and gradually building up a knowledge base to move forward. We’re most likely talking about rural survivors, as the big cities have been bombed out. In a way it’s a mercy that so many of the city population is wiped out at first, because agriculture is going to be radically reduced without regular oil supplies. Growing their own food will be the main technical and social concern for the first few years.
Surviving tradespeople like plumbers and carpenters and electricians would really be in demand! In some ways their next 'industrial revolution' would be much faster than the first industrial revolution, as we have already know the laws of physics and chemistry and biology that make the modern world possible. The mechanics and techs from the village would wait a while for the radiation to burn off in the big cities, and after a few months start exploring the ruins.
Petroleum only stores for about a year at most and then separates out so that it doesn’t work properly in a car engine. Wood gas engines can cook up fuel for priority engines like the harvester or tractor. Most transport would go back to cycling and horse drawn carriages - for a while. Rural villages would be mainly places where you walk and cycle for a the first few years. Let’s not forget that one man on a bicycle with a trailer can cycle a good 50km in a day to salvage some items. We might even see rickshaws make a comeback to transport the injured or elderly.
Technicians would be able to make local wind turbines and salvage solar panels for their workshops, and would also scavenge the tools and manuals that make them work. Even rural areas would have heaps of useless cars scattered around that could be scrapped for various metals for years to come.
There are primitive solutions for batteries and even refrigeration, so that life in a post-apocalyptic village with enough food and technicians could soon start to have some of the comforts of the modern world. Crucially, they’re salvaging knowledge, whether it is in books and manuals or DVD’s and hard drives. They'd get things up and running eventually, even if the local workshop had to stop working on cloudy days because their solar panels maxed out.
Bit by bit society would build up again, but in a more walkable, human based city plan. Energy would be more valuable and prioritised for the most important survival and salvaging efforts. Finally, some regions might rebuild the local hydro dams or get the nuclear power plants running again. Once they get breeder reactors up and running, any nuclear waste in that country becomes an incredible asset that could power the reformed nation for centuries to come. For more detail, see Isaac Arthur on Post Apocalyptic civilisations. The bottom line? I think within a generation or two, civilisation would be back - in a different shape and with much more energy efficient town plans, but back. What direction do you think it would take after rising from the ashes?