The problem with that is that "tactical nukes" aren't likely to kill in the same way the Hydrogen bombs did or the big nukes would. It would probably be more like generating a new Chernobyl type region. Except, they wouldn't be able to seal every site in a concrete sarcophagus. Imagine Ukraine with a dozen cities like Chernobyl in their country. Imagine the millions of Ukranians dying slow deaths from unending radiation poisoning. Imagine the drift to neighboring countries.