North Korea``s policy on nuclear and missile as its near term goal is to secure a nuclear state like Pakistan case since the miniaturization of nuclear warhead and reentry technology of missile should be achieved. North Korea``s mid and long term goal is to superficially cooperate with its denuclearization by reducing the number of nuclear warhead along with retaining substantial nuclear arsenal in the clandestine manner. They will attempt to remove international sanction toward North Korea. Then, signing a peace treaty, North Korea will eventually achieve its goal by the pull-out of U.S. forces in Korea and dissolution of UN Command. In the meantime, North Korea``s national strategy is to build a strong and prosperous country in terms of its immediate objective and to communize the Korean peninsular by implementing Kim Ilsungism and Kim Jongilism for the whole society as its final objective. To seek North Korea``s national strategy, once they estimate that the situation will be mature, Kim Jong-un will wage unification war by preemptive strike with nuclear and missile arsenal. We should be aware that North Korea``s nuclear and missile will be core warfighting assets of dismantlement of the division on the peninsula as Kim Jong-un``s new reshaping strategic initiative. In that context, deployment of THAAD on the peninsula is essential to neutralize attack by North Korea``s nuclear delivered by missile. There is no doubt on the need and justification of THAAD deployment in terms of North Korea``s strategy for unification war as well as North Korea``s policy on nuclear and missile. Simultaneously considering potential adverse effect of THAAD deployment, several conditions should be met. First, a site of THAAD``s position should be selected and constructed on the base of operational employment and residents safety. During the Key Resolve Exercise, THAAD system could be deployed in order to test THAAD``s operational effectiveness, it will be followed by operational deployment of THAAD to the site. Second, the ROK should establish Kill-chain and Korea Air Missile Defense(KAMD) system earlier than pre-planned project. Much more budget and military scientists should be reinforced in order to cope with North Korea``s nuclear and missile threat. Third, the Republic of Korea government should officially continue to proclaim that South Korea will not join Missile Defense led by the U.S. In that sense, instead of THAAD systems, the ROK should accelerate KAMD. Finally, If China and Russia will make every effort to denuclearize North Korea and North Korea will abandon its nuclear and missile arsenal, THAAD system``s withdrawal will simultaneously be implemented. In particular, it is much more important for the Republic of Korea to shift from its defensive posture to offensive security posture including preemptive strategy and military power in order to challenge a national crisis from North Korea``s increasingly, direct nuclear and missile threat.