The Chaldeans are Eastern-rite Catholics - autonomous Churches of Eastern origin which retain their own liturgy and traditions, but recognise the Pope's authority.
Its biggest components were made up of urban Catholics plus recent descendants of Eastern European Jews and southern Democrats, who were Protestant and openly racist.
He apologised to Jews for Catholic passivity during the Holocaust, prayed at a Syrian mosque and took steps to heal the rift between Catholics and adherents of the various eastern Orthodox churches.