"The calculus for small countries like North Korea is not hard to understand.
On the one hand, they see the nuclear powers not moving toward disarmament as planned.
On the other, they see countries like the United States routinely sweeping into countries like Libya and Iraq – who either abandoned or never started nuke defense programs – to pursue "regime change" policies.
As such, many smaller countries may feel like developing nukes is the only way to ensure their sovereignty. This pushes us into situations like this mess with North Korea."