The main focus of detailed discussions in this essay was studying the reasons that caused Syria to turn into an important security issue for Iran. Given the long history of relations between the two, the emergence of this crisis has activated Iran heavily and roughly to prevent and confront the West's power since lagging in this issue will impose heavy prices on the Islamic Republic of Iran. The current essay has studied four important reasons for the security importance of Syria to Iran; Syria as a dam against the infiltration of the US anti-Iran policies in the Middle-East, Syria's common borders with Hezbollah and Israel, Syria as a place for adopting ideological defense-invasion strategy and its stance in the confluence point of the Islamic Iran and the Arab nationalism ideologies can be the main elements for forming Iran-Syrian security relations. As Iran's ally, Syria can be a key factor in preventing the West's complete plundering of the region and given the four aforementioned components, it can justify and redefine Iran's all-out support for Syria during the crisis in the country.
