In the opening of Luke’s description of Jesus’ birth, Luke begins to assimilate language used to describe the Emperor of Rome at the time, Caesar Augustus. As Sri explains, “In the eyes of many, Augustus saved Rome from destruction. He was thus hailed as “savior of the whole world,” for he ushered in a new age—the age of the Pax Romana (the Roman peace). He eventually was called “son of God” and worshiped as a deity. His date of birth even was celebrated in some parts of the empire as “the birthday of the god,” for his coming was said to bring “good news” for the whole world. “
Naturally, it is important to point out to 21st century peoples that a political leader during the 1st century A.D. in Rome was not merely seen as such, but rather as Pope Benedict explains, “Augustus was regarded not just as a politician, but as a theological figure—which shows that our distinction between politics and religion, between politics and theology, simply did not exist in the ancient world. In the year 27 B.C., three years after his assumption of office, the Roman Senate had already awarded him the title Augustus (in Greek: sebastós)—meaning “one worthy of adoration.”
Of course, the Gospel writers incorporated even more of the political speech of the period into their publications, in Pope Benedict’s first volume of his Christological discourse the faith, Jesus of Nazareth: From the Baptism of the Jordan to the Transfiguration, he explains:
“The messages issued by the emperor were called in Latin evangelium, regardless of whether or not their content was particularly cheerful and pleasant. The idea was that what comes from the emperor is a saving message, that it is not just a piece of news, but a change of the world for the better. When the Evangelists adopt this word, and it thereby becomes the generic name for their writings, what they mean to tell us is this: What the emperors, who pretend to be gods, illegitimately claim, really occurs here—a message endowed with plenary authority, a message that is not just talk, but reality. In the vocabulary of contemporary linguistic theory, we would say that the evangelium, the Gospel, is not just informative speech, but performative speech—not just the imparting of information, but action, efficacious power that enters into the world to save and transform. Mark speaks of the “Gospel of God,” the point being that it is not the emperors who can save the world, but God.”
So, naturally, as Luke assimilates the language of the empire into his Gospel, he forms a narrative that describes God’s salvific plan, which is quite different from that of Augustus, as one of raising the lowly and the marginalized, either by material and/or spiritual means of all nations, and it is encompassed in the great Magnificant of Mary:
51 He has shown strength with his arm,
he has scattered the proud in the imagination of their hearts,
52 he has put down the mighty from their thrones,
and exalted those of low degree;
53 he has filled the hungry with good things,
and the rich he has sent empty away. 
 Edward Sri, Dawn of the Messiah: The Coming of Christ in Scripture (Cincinnati: St. Anthony Messenger Press, 2005), 69.
 Pope Benedict XVI, Jesus of Nazareth: The Infancy Narratives (New York: Image, 2012), 60.
 Pope Benedict XVI, Jesus of Nazareth: From the Baptism of the Jordan to the Transfiguration (San Francisco: Ignatius Press, 2007), 46-47.
 RSV Lk 1:51–53.