Im inclined to say that nuclear war WILL happen eventually, even if it is started by a stupid accident.
The problem is that so many nations are now armed or actively trying to arm themeselves with nuclear weapons, that eventually nukes are going to be a relatively common threat from any nation.
For instance, say N. Korea decides to demonstrate their nuclear ability by striking a NATO, UN, or Allied installation. If N. Korea went nuclear, then the country attacked would retaliate in kind no doubt, potentially instigating action against the retaliator, forcing another nuclear country to launch.
Ultimately, if the US or Russia become involved, then the world will probably fall under the MAD (Mutually Assured Destruction) principle of the Cold War.
This example was a country to country threat.
The Terrorist to country threat is far nicer by comparison.
Say for example, Al-Queda received a nuclear device. Now, they could target any single place they wanted, or, if they were half as smart as we hope they arent, they could divide the material amongst several suicide bombers and create dirty bomb explosions in multiple places, ranging from Israel, to the UK, to finally the US.
Remember, terrorists, espically Al-Queda, no longer have anything to lose because they know that if we find them, we will destroy them or have them destroyed.
The worst nuclear threat is posed by the detonation of a poor mans nuclear weapon in a city that will spread radioactive material around the area and cause fallout that poses serious risks.
