ABSTRACT Changes and an increase in military spending ASEAN countries is the fact dynamics armament Southeast Asia today. Nevertheless, on the other hand countries in Southeast Asia seek to "create" peace through regional collaborations to always maintain regional peace. Both are dynamics that give rise to ambiguity Southeast Asian regional security, will Armament dynamics will disrupt stability of Southeast Asia, or otherwise become a way of supporting peace-East Asia Region. So this thesis study posed two research questions: (1) why the ASEAN countries to modernize our military posture? (2) What are the implications of modernization of the military posture toward peace in Southeast Asia? To answer the second question, this study uses the Realist paradigm by applying two concepts, namely the Security Dilemma and the Balance of Power. Based on the formulation of the problem, research questions and methodologies used by the writer, this thesis put forward two hypotheses, the first ASEAN countries to modernize our military posture as alert as a reaction to the case of uncertainty the South China Sea, as it also indirectly led to opportunities that ASEAN member States do weapons development and also issues of domestic security interests of the six ASEAN countries themselves. Second, that the construction of military force by the State-states of ASEAN will maintain peace in the region, because supplies military posture will put all ASEAN countries and the absence of parallel military force dominates. Despite the absence of war is not to say they trust each other. The mechanism of peace in Southeast Asia will be more easily achieved because the elements of balance of power between the ASEAN Member. First, the six major countries of ASEAN is qualitatively conduct weapons development, but it is not categorized as an arms race that is not harmful. This is reflected in the lack of initiative from the sixth to attack or hostile states with other countries. ASEAN countries to modernize our military posture for the military on alert security dilemma posed by a further warming of the reaction of the South China Sea case, as it also relates to ASEAN and also domestic issues as well as the security interests of each of the six ASEAN countries. Second, the impact of weapons modernization sixth ASEAN countries will maintain peace in the region. Maintenance of regional peace for completeness military posture will put all ASEAN countries and the absence of parallel military force dominates. But it is undeniable that the current military force as a tool that enhances the prestige of confidence every ASEAN countries, it is increasingly difficult for effective problem-solving mechanisms such as TAC, and ARF, because each State to the dispute feel stronger militarily. Despite the absence of war does not mean that ASEAN countries trust each other. Each State is still a military alert because conflict of history and sensitivity of allied countries. Keywords : Security dilemma , ASEAN, Arms Build-up, ASEAN, Arms Race.