After the World War II, the Prohibition of using the Force’s Principle was established in international law as Jus Cogens and then equal to Charter’s contents, the states were forced to disregard the use of force in all forms. However, some exceptions were looked among charter’s articles that on the basis of them, the states could enjoy using force’s right in these cases. One of these instances was “Self-Defense” that on the basis of which, when there was an attack on the states, they had the right to use the force for the abatement of aggression and self-defense.

Meanwhile, one of the strategies formed in Cold War Era, was the Strategy of Preemptive War (Defense). On the basis of special commentary of Charter’s Article 51 that some states performed, this strategy was used.  The incidence of 11 September Accident was a turning point that caused this strategy to be brought forth for discussion in an international level. Also, this accident paved the way for the White House authorities to use this strategy to legalize their Afghanistan & Iraq military invasions.

Therefore, in this study, an effort has been made to explain the Preemptive War Strategy theoretically, appraising the legitimacy of this war through the international law and its effect or influences on the international relations.