While the winds of an Iraq war are gusting ominously, peace advocates from across the religious and ethnic spectrum are joining forces. Pope John Paul II turned more than a few heads on Valentine's Day by hosting Iraqi Deputy Prime Minister Tariq Aziz at the Vatican and asking God to bless Iraq. But these two men share more than just a desire to avoid war: Aziz is a baptized Chaldean Catholic—Iraq's branch of Roman Catholicism.

Given the ruthless and bloody history of Iraq's Ba'athist regime, critics have questioned Aziz's Christian credentials. Still, the high profile of a Catholic in Saddam Hussein's overwhelmingly Sunni Muslim government has become a source of intrigue and curiosity. And it raises the larger question: How has Christianity fared in the history of Iraq—the geographic area that was once Mesopotamia? A few weeks ago we examined the origins of Iraq's Christian minority from Pentecost until Constantine's conversion in A.D. 312. Now we pick up their history from there.

Despite severe Persian Empire persecution, the ancient Mesopotamian Church blossomed during the fourth century while allied with Antioch, which was a major early hub of Christianity in the Roman Empire. In A.D. 410, at the Council of Seleucia, the Persian church declared its separation from Antioch.

Soon after, these Persian Christians fell under the influence of Nestorian teachings. Nestorius (d. 451), a patriarch of Constantinople, was condemned as a heretic by the Roman Church for leading his followers to question Jesus' dual nature as fully God and fully man. Many scholars of theology now believe poor Nestorius was more misguided than mischievous. He did not intend to separate the divine and human natures of Christ into distinct persons. But ...