The 2003 US-led invasion that toppled Saddam Hussein's Sunni-dominated Baathist government inaugurated a new sectarian political order in which Shia parties, representing Iraq's demographic majority, gained dominant power for the first time in the modern state's history, formalized through an informal power-sharing arrangement allocating the presidency to a Kurd, the premiership to a Shia Arab and the parliamentary speakership to a Sunni Arab. This transition fueled a brutal sectarian civil conflict between roughly 2006 and 2008, with Sunni and Shia militias targeting each other's civilian communities, and later provided fertile ground for the Islamic State's 2014 seizure of Sunni-majority Mosul and much of northern and western Iraq.
The Islamic State's campaign against the Yazidis, a Kurdish-speaking religious minority with a syncretic faith drawing on Zoroastrian, Christian and Islamic elements, included mass killing and enslavement in 2014 that the United Nations has recognized as genocide, devastating a community centered on the Sinjar region.
Iraq's ancient Christian population, predominantly Chaldean Catholic and Assyrian Church of the East communities concentrated in the Nineveh Plain, and the small Mandaean community, practitioners of a Gnostic Baptist religion tied closely to John the Baptist, have both shrunk by a large majority since 2003 through emigration driven by violence and displacement.