As of 2001 when the Shanghai Cooperation Organization (SCO) was established, an important issue was the reaction of regional and beyond regional actors especially that of big powers. Contrary to its traditional policy of not joining any regional security organization, Iran determined to apply for full membership in the SCO, thus achieving the status of an observer member in 2005. The present article seeks to answer the question why Iran changed its traditional policy and sought to join the SCO? In other words, the main question is: what have been the principal factors which shaped Iran's policy towards the SCO? Our main hypothesis is that consequent upon some fundamental changes in the structure of international system since 2001, Iran sought to use what we term the “structural opportunity” and to join the SCO. Iran seeks not only to guarantee its national security, but also to project the image of a powerful country in the Greater Middle East region.
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