This chapter analyses the role of external actors in relation to the Syrian conflict. It uses the theoretical lens of the so-called Regional Security Complex Theory by Barry Buzan and Ole Wæver. It looks at each of the state and sub-state actors in turn. It also identifies salient issues that need to be settled between them in order to stabilize Syria, as well as predicting some possible future scenarios. It concludes that the new Middle East regional security complex will no longer be dominated by the one remaining true global power, the US, as it was in the past, but will be defined much more by the relative power relations among the Middle Eastern regional great power states: Turkey, Iran and Israel, as well as by Russia, which is a much more flexible player and will be able to make use of the criss-crossing amity–enmity relations among the states of the region.