The “security dilemma” in action: Iran wants S-300 surface-to-air missiles (SAMs) to defend itself against potential US or Israeli airstrikes. At the same time though, the S-300 systems make the Gulf Cooperation Council (GCC) states feel insecure because they threaten GCC-based civilian and military air traffic. Undoubtedly the GCC will appeal to the United States for more/better air-power and support, creating more tensions between Iran and the US. In the end, everyone is less secure….
https://www.rusi.org/publications/defencesystems/ref:A554385A7EAF10/#.VUOl_pOrHSg
IR Theory & Practice 