BAGHDAD (AP) — The new patriarch of one of the most important Christian churches in the Middle East assumed his duties Friday in the Iraqi capital weeks after he was elected for the post.

Polis III Nona, who was born Amel Shamoon Nona, 58, replaced Cardinal Louis Sako of the Chaldean Catholic Church, who stepped down in March saying he had asked to retire to pursue “prayer, writing and simple service.”

The new patriarch previously served as the Archbishop of the northern Iraqi city of Mosul and the Archbishop of Sydney, before becoming the patriarch for the Chaldean Catholic Church in Iraq and the World.

He was elected on April 12, a month after Sako, 76, retired.

Partriach Nona’s inauguration comes at a time when the numbers of Christians in Iraq have been dropping since the 2003 U.S.-led invasion that toppled Saddam Hussein and the rise of the Islamic State group before they were defeated.

During the rule of IS that declared a caliphate in large parts of Iraq and Syria, Christians suffered discrimination and churches were blown up by the extremists.

IS was defeated in Iraq in 2017 and two years later in Syria.

The Chaldean Catholic Church is one of the nearly two dozen Eastern Rite churches that are in full communion with Rome. It is one of the four that claim links to the ancient Church of the East, located in Mesopotamia, and is today prevalent in Iraq, Iran and Lebanon, as well as in the diaspora.

The number of Christians in Iraq today is estimated at 150,000, compared with 1.5 million in 2003. Iraq’s total population is more than 40 million.