James Ussher was the Archbishop of Armagh (present-day Ireland) as well as the Vice-Chancellor of Dublin's Trinity College. His goal in writing his Annals of the World was linking the Bible to secular works of recorded history, thus presenting a unified account of the history of the world from this perspective. His meticulous work on the book reportedly began as early as the summer of 1640. Part of his reason for this ambitious work was his purported dream of establishing the superiority of the Protestant clergy's scholarship over that of the Jesuits, the Catholic church's intellectual order.
The chronology for which Ussher's Annals of the World was famous gave detailed and dated accounts of world events starting from creation to 70 AD, when the Roman Emperor Titus destroyed the Temple of Jerusalem. Subtitled "The Origin of Time, and Continued to the Beginning of the Emperor Vespasian's Reign and the Total Destruction and Abolition of the Temple and Commonwealth of the Jews," the Annals established the chronology of the Bible through the use of internal clues in the Old Testament --- such as genealogies, biographies, lists of kings and fulfilled prophecies.
Ussher used the Bible as his standard source, and chose the Masoretic Text of the Old Testament as his basis for dating because of its closeness to the original. He also drew heavily from as many primary sources as he could gather and examine, traveling as far as the Mediterranean for his research. His extra-Biblical sources included astronomical records --- a method known to be reliable for uniting separate chronologies --- as well as the works of Josephus, Manetho and other ancient historians. He also took Greek mythology and Assyrian history into account when drafting his chronology.
Ussher's work today remains highly ridiculed in creation versus evolution debates, both by Christians and non-Christians. The main point of contention is the date he established for the creation of the universe, which sets its age at a mere 6,000 years old --- an estimate which has since been disproven to many by science. The reliability of the Annals has also been questioned due to some methods Ussher used in establishing his chronology, such as his choice to back-calculate the date of the Genesis events from the death of Nebuchadnezzar II instead of relying on archaeological theories involving the Fall of Jerusalem. All this stems from his firm belief in the Bible's historical accuracy --- a divisive issue even to this day.