Like all SF fans, I have given much thought to how things will turn out after a collapse of civilization. I don't claim to have any special insight, but there are some historical examples we can use as a guide. The Roman empire collapsed, although "collapse" may be an exaggeration, it took hundreds of years to finally cave in, and although Roman civilization certainly gave way to the Dark Ages in Europe, the continent did not relapse into barbarism.

Before the Romans, they Mycenaean civilization of the Eastern Mediterranean vanished (probably because of the volcanic eruption and tsunami of Thera), and Greece had its Dark Age and barbarian invaders. People still remembered how to read and write, work metals, raise livestock, construct buildings, build and sail ships, weave cloth, farm. Things didn't slide back to caveman status. Also, there was contact with other civilizations, the Byzantine empire held out for almost another thousand years after the fall of Rome, and the Arab civilization preserved much of what we still remember of the Roman world.

China has gone through multiple collapses through its long history, but it always seemed to recover. India has had many ruling civilizations, but it has remained civilized. The Egyptian civilization eventually disappeared, although it managed to last as long as everyone else put together! Other civilizations, such as the Amerind cultures of the Andes, Central America and Mexico kept on recovering from various disasters until the Spaniards succeeded in crushing them altogether.

It appears that as long as people can still farm, make metal tools and weapons, and construct buildings and carry on trade, some sort of village culture, leading to feudalism and city-states will take over.

What concerns me is that in our civilization, these basic village tasks are now beyond the capability of everyone except a few hobbyists. Even farmers today can't farm the way they did a century ago, we've become addicted to farm machinery, chemicals, irrigation and seed, and not enough people today actually know how to use oxen and plow to grow food, much less have the gear and animals. Making cloth, mining and smelting metals, constructing buildings, even starting a fire without matches is beyond the skill level of most of us (myself included).

I fear modern man has become so addicted to his technology that he may not be able to recover to a neolithic slash-and-burn agricultural village or even nomadic hunter-gatherer level after the fall. After what little ammunition and game there still is available is exhausted, I fear we will relapse to cannibalism, and the survivors of that will eventually stabilize at some paleolithic level.

My guess as to which modern nation will be most likely to survive an end-of-civilization scenario, restabilize at the agricultural village level, and eventually recover to some form of pre-technological civilization: India.