The American policy of nuclear arms reduction and stressing conventional weapons, including its missile defense system and its role in nuclear deterrence, pose numerous questions on the aims and consequences of the deployment of such a system. Among these questions are whether this system is able to realize nuclear deterrence and what the impact of its deployment would be on security-military behaviors of other states and specifically that of the Islamic Republic of Iran. On the same basis, the main question of this essay is if the missile defense system canestablish nuclear deterrence? The hypothesis put to the test is that the missile defense system cannot play a considerable part in the creation of nuclear deterrence by itself, and that as far as the consequences are concerned, it could fuel an arms race and deteriorate security and stability. The section on consequences argues how the missile system instigates foes and main rivals, provokes peripheral circles of enemies and main competitors, and promotes perceptions of U.S. strategy as offensive rather than defensive. As the confronting of a possible offensive by Iran is declared as one of the aims of the U.S.missile defense shield in Europe, the subsidiary question deals with the potential effect the deployment of the missile defense systemcould have on the security-military behavior of Iran. This paper asserts that the deployment of the system extends perceived insecurity on the part of Iran and pushes the Islamic Republic towards adopting a “reciprocal defensive strategy” or “reciprocal offensive strategy”.