The fallout from nuclear war would be much worse than the explosions of said nuclear war themselves. In many countries especially in higher latitudes it would be a hugely devastating after years of all the food. A new nature food study suggests that a war between the US and Russia with most of those nuclear weapons being used would lead to as many as 150 million tons of soot being ejected into the atmosphere via all that smoke. That would then really cause the climate to cool and they believe it would actually reduce the amount of calories that agriculture around the world could produce by something like 90 percent.