Any nuclear exchange between any nations, or groups of nations, would have catastrophic results. Today, there are two nations talking carelessly about the use of nuclear weopons. One has them, North Korea, the other may have them shortly, Iran.
In Iran, the people running that nation have already stated their intention of wiping out Isreal. Now whatever you think of the nation of Isreal, that people there, in the memory of some still living, have seen the results when someone stating the intention of wiping out the Jewish nation. Add a nuclear capability, and that threat takes on a reality that is truly dangerous.