The face stares out from multiple billboards in central Baghdad, a grey-haired general casting a watchful eye across the Iraqi capital. This military commander is not Iraqi, though. He's Iranian. The posters are a recent arrival, reflecting the influence Iran now wields in Baghdad. Iraq is a mainly Arab country. Its citizens, Shi'ite and Sunni Muslims alike, have long mistrusted Iran, the Persian nation to the east. But as Baghdad struggles to fight the Sunni extremist group Islamic State, many Shi'ite Iraqis now look to Iran, a Shi'ite theocracy, as their main ally. In particular, Iraqi Shi'ites have grown to trust the powerful Iranian-backed militias that have taken charge since the Iraqi army deserted en masse last summer. Dozens of paramilitary groups have united under a secretive branch of the Iraqi government called the Popular Mobilisation Committee, or Hashid Shaabi. Created by Prime Minister Haider al-Abadi’s predecessor Nuri al-Maliki, the official body now takes the lead role in many of Iraq's security operations. From its position at the nexus between Tehran, the Iraqi government, and the militias, it is increasingly influential in determining the country's future. Until now, little has been known about the body. But in a series of interviews with Reuters, key Iraqi figures inside Hashid Shaabi have detailed the ways the paramilitary groups, Baghdad and Iran collaborate, and the role Iranian advisers play both inside the group and on the frontlines.