Missile defense is a system, weapon, or technology involved in the detection, tracking, interception, and destruction of attacking missiles. It is a naval weaponry which provides a defense system. Originally conceived as a defence against nuclear-armed Intercontinental ballistic missiles (ICBMs), its application has broadened to include shorter-ranged non-nuclear tactical and theater missiles. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information