The collapse of the bipolar system made necessary the revision of the concept of security. The inability of the mainstream thoughts to define the concept of security in a broad and multi-dimensional manner, led to the emergence of new theoretical schools in the field of international relations. The Copenhagen School is one of these theoretical schools. This school studies the national security of countries at the regional level. One of the things that will have a major impact on national security, is the regional security system quality. The regional security structure of state is formed within a particular geographic area with the aim of securing the region. The formation of regional security structures can also promote actors, national security. This article adopts constructivist approach in the context of a regional security system and applies the security theory developed "Barry Buzan". It uses causal explanation to explore the Persian Gulf regional security system in the post-saddam era and its effect on the national security of Iraq. It also examines the role of regional powers and the U.S. in createing this new order. Results reveal that regional security system in the post-Saddam period is based on the balance of power between Iran and Saudi Arabia. This new order intensified the ethno-religious competition in the domestic scene of Iraq and led to the failure of state-building process and foreign policy goals in Iraq. But the presence of extra-regional powers such as the United States, as the creator of the new balance of power in this country dealt a blow to its national security. The main objective of article is to show the trends and factors involved in the formation of a new security order and to examine the consequences of this order for the national security of Iraq.
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