In the background of the strike stands Iran's attempt to construct a network of friendly forces stretching from Iraq through Syria to Hezbollah in Lebanon. In 2016, pro-western sources in Iraq warned that Iran was building just such a conduit. In December 2017, The New Arab reported that convoys of unmarked vehicle had passed into Syria from Iraq through checkpoints manned by the Hashd al-Shaabi, the mostly Shi'ite militias that are known as Popular Mobilization Units (PMU).