Russia–Syria–Iran–Iraq coalition

The Russia–Syria–Iran–Iraq coalition (RSII coalition), also referred to as 4+1 (in which the "plus one" refers to Hezbollah of Lebanon), was a joint intelligence-sharing cooperation between opponents of the Islamic State (IS) with operation rooms in Syria's Damascus and Iraq's Green Zone in Baghdad. It was formed as a consequence of an agreement reached at the end of September 2015 between Russia, Iran, Iraq and the Syrian Arab Republic to "help and cooperate in collecting information about the terrorist Daesh group" (ISIS) with a view to combatting the advances of the group, according to the statement issued by the Iraqi Joint Operations Command. The statement also cited "the increasing concern from Russia about thousands of Russian terrorists committing criminal acts within ISIS."

In October 2015, it was suggested that the Russia–Syria–Iran–Iraq coalition may have been devised during the visit by Qasem Soleimani, commander of the Iranian Quds Force, to Moscow in July 2015. During the early days of the operation, the Russian Air Force were backed by the Syrian Armed Forces, Iranian Islamic Revolutionary Guard Corps, and other allied militias. The United States of America has been particularly hostile to the activities of Iran, Russia and Hezbollah in Syria since the start of the civil war, have criticized this coalition.

After the fall of the Assad regime in Syria and the withdrawal of Iran from the country, it is unclear if the alliance is still active as it could possibly be dissolved.