Augustine of Hippo. He convinced Orosius to write his history.
Paul Orosius defended Christianity against false teachings and wrote a history backing up Augustine's book The City of God. His history had some original material in it covering events in his own age, which makes it valuable to historians today.
Orosius was a native of Tarragona in Spain. When the Alani and Vandals invaded Spain in A.D. 409, he narrowly escaped their violence. But his real concern was for the church. A false teaching with elements of gnosticism and Manicheaism spread in Spain. Those who resisted the heresy did so using a book of Origen's which had serious errors of its own. On his own initiative, Orosius traveled to North Africa in A.D. 415 to consult with Augustine of Hippo on the best way to fight these errors which had to do with the nature of Christ, God, and man.
Augustine was impressed with Orosius. He spoke of him as young in years, but a presbyter in rank—zealous, alert in intellect, ready of speech, and fitted to be useful in the work of the Lord. Augustine wasn't much help to Orosius, but sent him to Palestine to consult with the famous scholar Jerome, who lived in the region where the errors arose.
Jerome received Orosius kindly. Soon, however, Orosius was called to attend a council in Jerusalem, where he also engaged in fighting another heresy, this one by Pelagius, which seems to have taught that people can save themselves.
The following year, Orosius returned to Africa. Augustine asked him to write a world history to back up his own book The City of God. Orosius did so, then proceeded towards Spain with relics that were thought to belong to the Stephen whose stoning is recorded in the Acts of the Apostles.
Orosius' book was not history as we know it, but more of an epitome. He quoted many authors and the Bible. Because it was written under the express sanction of St. Augustine, in a pleasing style and at convenient length, and was recommended by church authorities as an orthodox Christian work, it became the standard text-book on the subject during the middle ages, and was heavily quoted by Bede and other medieval writers. However, historical standards were low then, and Orosius made many mistakes, both as to facts and numbers, and his system of chronology was faulty.
Nonetheless, his concern for the church and its heritage of belief has given him a lasting name which he otherwise would not have had.