A couple of notes on fallout. It's important to remember that the vast majority of strikes outside central Europe will be airburst detonations. They'll be exploding at 10,000 feet or so in order to ensure the largest possible fireball and widest possible area of destruction. These strikes are perfect for things like airfields, cities, and troop concentrations, and are the most common type of strike. All fallout is is irradiated debris carried into the upper atmosphere by the updraft created by the mushroom cloud. It's not automatically created by the bomb, except for the few bits of bomb casing that aren't immediately vaporized. Because airbursts explode high off the ground, there isn't as much opportunity to create fallout. If you read detailed accounts of the two Japanese detonations, you'll find that there was very little radiation outside the initial blast zone. Most fallout was precipitated in rain from the detonations and occured within a few miles of the blast zone. That's going to be the case here. Now, most of the tactical strikes, and the bomber strikes going after buried bunkers are going to create fallout. Many of the artillery-shell fired weapons and the man-portable weapons have contact detonators, which means they explode on contact with the ground. Lots of fallout will result from that. A third source of fallout will come from strikes on nuclear reactors -- conventional or not. The destruction of the Arco, Idaho reactor in the United States will create more fallout than every other strike on the United States and Canada combined. All the rest are airburst detonations. In the Soviet Union, there are going to be a lot more strikes on nuclear reactors. Its a two-fer. You not only destroy the nearby city with an airburst, but also release massive clouds of radiation by breaching the reactor. Imagine dozens of Chernobyls scattered across Europe and Asia on top of the fact that you've just had a nuclear war. Ghastly stuff. In the long run, however, fallout will decay quickly. The really deadly stuff has a half-life measured in hours. That isn't good for folks in central Europe or the former USSR, but it is good news for people in Africa, the Middle East, Asia, Australia, and South America. The oceans also do a remarkably good job of soaking up radiation. By the time an ocean current takes bomb fallout anywhere close to an untouched shore, the radiation will have decayed to a safe level. Radiation strong enough to be harmful will kill any effected fish, though it is possible that some radioactive fish will survive in the ocean. Someone in South America eating that fish wouldn't get any more of a radioactive dose than he or she is probably already getting from the sun and air. Rain and snow concentrate fallout very well, however. Scattered fallout particles in the air that normally wouldn't kill a person are concentrated in rain, and if they fall on you ... well, you won't have time to worry about being wet for too long. That's going to be the real danger for folks in the former USSR and Scandinavia. If it's raining in their area shortly after the war, you not only have to seek shelter, but you're probably going to have to move, since the rain will have contaminated nearby lakes, streams, and rivers to an unsafe level. Radioactive river runoff (say that ten times fast) is going to concentrate in places like the Caspian Sea, Aral Sea, and Black Sea. The Baltic Sea, too, will also suffer. It's not the fallout that gets you -- it's the concentration of fallout. Think of how many blasts took place in Germany. Then imagine rain falling, carrying all that radioactive runoff into the Rhine, the Elbe, the Weser, and so on. The rivers carry that into the Baltic or the North Sea, and then you've got problems. For weeks or months, it's not going to be safe to fish in those areas. I'm not sure how long -- no one's ever been able to do a study on that scale, but I'll tend to favor the weeks end of things.