Given my earlier post about realism, I should give those folks their due. When I learned of the Security Dilemma, one of the key foundations of realism, the world became more more comphrensible.
The SD essentially states that in the pursuit of security, any one country's effort to improve its security will threaten others, causing the others to ramp up their efforts to improve their security, threatening the first country. So, the dilemma is that any unilateral effort to improve one's security ultimately fails, often leaving one and all worse off. Suddenly, arms races made complete sense to me, without needing to invoke military-industrial complexes.
Why raise this now? Because Iran has objected to the activation of NATO missile defense systems in Turkey. Sure, NATO can say this is a purely defensive measure, which it really is, but being better able to thwart Iranian missiles means that the costs of attacking Iran decline. This is also why the Soviet Union was so upset about the Strategic Defense Initiative--if one has a shield, one can more easier use one's sword especially if the other guy does not have a shield.
So, score one for Realism, as we see the Security Dilemma play out quite clearly.