BEIRUT/BAGHDAD - Iraqi Shi'ite Muslim militias fighting in Syria have started returning home to combat a lightning advance by Sunni insurgents in their own country, an exodus that could affect the balance of power in Syria.
The movement demonstrates how intertwined the conflicts in the two neighboring countries have become, as Sunni and Shi'ite fighters move between them and shifts in battlefield momentum on one side of the border influence the other.
President Bashar Assad has relied heavily on Iranian-backed Shi'ite militias from Iraq and Lebanon to help turn the tide against overwhelmingly Sunni rebels.