But it wasn’t for a week or two afterward that people began dying from lack of an immune system. The intense burst of radiation had destroyed their bone marrow, and without a functioning immune system, the Japanese were defenseless against the onslaught of germs our bodies slough off every day. The loss of platelets caused them to suffer and die from internal hemorrhage.
“Duck and cover” worked if you were outside the main blast area and likely to survive anyway. Concrete shelters provided some protection closer in. But while they enhanced survivability for people, the point was that a thermonuclear exchange between the United States and Soviet Union was going to destroy the nation’s industrial and commercial fabric. Surviving the blast didn’t mean surviving a year.
The USSR placed more emphasis on a robust Civil Defense program than the United States. They believed they could actually come out of a nuclear exchange with a damaged, but still functioning country. I guess their World War 2 experience with the Germans led to that line of thinking. I doubt it would have been effective. A nuclear exchange will simultaneously and immediately eliminate all major economic nodes. The result would still have been catastrophic.