The Vatican hopes that the landmark visit will rally the country’s Christian communities and encourage them to stay despite decades of war and instability. Francis has also delivered a message of interreligious tolerance and fraternity to Muslim leaders, including in an historic meeting Saturday with Iraq’s top Shiite cleric, Grand Ayatollah Ali al-Sistani.

Francis will head to the northern city of Mosul, which was heavily damaged in the war against IS, to pray for Iraq's war victims. The setting will be a city square surrounded by the remnants of four damaged churches belonging to some of Iraq’s myriad Christian rites and denominations.

He will travel by helicopter across the Nineveh plains to the small Christian community of Qaraqosh, where only a fraction of families have returned after fleeing the IS onslaught in 2014. He will hear testimonies from residents and pray in the Church of the Immaculate Conception, which was torched by IS and restored in recent years.

He wraps up the day with a Mass in the stadium in Irbil, in the semi-autonomous northern Kurdish region, that is expected to draw as many as 10,000 people. He arrived in Irbil early Sunday, where he was greeted by children in traditional dress and one outfitted as a pope.

Iraq declared victory over IS in 2017, and while the extremist group no longer controls any territory it still carries out sporadic attacks, especially in the north. The country has also seen a series of recent rocket attacks by Iran-backed militias against U.S. targets, violence linked to tensions between Washington and Tehran.

The IS group's brutal three-year rule of much of northern and western Iraq, and the grueling campaign against it, left a vast swathe of destruction. Reconstruction efforts have stalled amid a years-long financial crisis, and entire neighborhoods remain in ruins. Many Iraqis have had to rebuild their homes at their own expense.

Iraq's Christian minority was hit especially hard. The militants forced them to choose among conversion, death or the payment of a special tax for non-Muslims. Thousands fled, leaving behind homes and churches that were destroyed or commandeered by the extremists.

Iraq's nearly 2,000-year-old Christian population had already rapidly dwindled, from around 1.5 million before the 2003 U.S.-led invasion that plunged the country into chaos to just a few hundred thousand today.

Francis hopes to deliver a message of hope, one underscored by the historic nature of the visit and the fact that it is his first international trip since the start of the coronavirus pandemic.

Public health experts had expressed concerns ahead of the trip that large gatherings could serve as super-spreader events for the coronavirus in a country suffering from a worsening outbreak where few have been vaccinated.

The Vatican has said it is taking precautions, including holding the Mass outdoors in a stadium that will only be partially filled. But throughout the visit, crowds have gathered in close proximity, with many people not wearing masks. The pope and members of his delegation have been vaccinated but most Iraqis have not.