Who is the shadowy Iraqi militia that attacked the UAE?

As tensions between the United Arab Emirates (UAE) and Iran-backed Houthi rebels over the war in Yemen continue to rise, a little-known armed group in Iraq has come to the fore. Calling itself Awliyat al-Wa'ad al-Haq, or the True Promise Brigades, the group claimed responsibility for a drone attack on the UAE on Wednesday, saying in a statement that it launched "four drones targeting vital facilities in Abu Dhabi" in retaliation for the Emirates' policies in Iraq and Yemen. The UAE's defence ministry said it had intercepted and destroyed three drones that penetrated the Gulf country's airspace over unpopulated areas on Wednesday. The attack was the latest in a series of aerial assaults on the Gulf state over the past few weeks. The previous three attacks were all claimed by Yemen's Houthi rebels.