Of all the threats to humanity, or at any rate to our continued progress, nuclear war is possibly the greatest, and maybe the only one with real significance.
As with religion, much has been written on this subject, and there is little that can be usefully added here, except to point out that globalization, whether economic, cultural or political, is the best possible way of avoiding clashes between nation states which might end in nuclear exchanges.
The world is right to be scared of a rogue nation such as North Korea which does not join in or benefit from global organizations. There are few of them, however, and the extending reach of the media will perhaps work to reduce their viability in the same way that it is working to open up countries closed off by sectarian curtains.
As a result of media intrusion, rogue governments and authoritarian, repressive regimes in general have become vulnerable to 'people power'. This is a new and hopeful phenomenon. Historically, revolutions were bourgeouis affairs, even if they carried democratic banners. It is only now, when whole populations have access to the whole, real world through television and the Internet, that they are armed with ideas that encourage them to protest or rise up against their tormentors. There are plenty of dictatorships left, still, but a far higher proportion of humanity lives under relatively free and even democratic regimes today than ever before, if China be excepted, where a sort of middle way allows the leadership to maintain a precarious hold on power. Not perhaps for very long, we may hope?
1 Smalley, R E, (2003) NANOTECHNOLOGY, the S&T Workforce, ENERGY & Prosperity, Podcast, Washington (Rice University)