The Missile Shield

Where may I find some rationale for the construction of a missile shield in Europe? I am serious. I mean, Iran does not have such missiles nor warheads. Furthermore, if Iran's president's quondam remarks be interpreted as threatening Israel, I do not remember a coda being added: "...and that goes fer Europe, too!" What is going on and why is no one questioning this? Do not say War on Terror, or I shall lose it. I suppose now the crazed mountain cave bearded blokes have missiles. What in the name of heaven is going on?