Why do you think Our Lord, the Son of God, decided to become man under the rule of the Roman Empire? Why was it Rome that crucified Him?
Out of all the periods of human history, why did God determine from all eternity that He should become man as a subject of imperial Rome during the pax Romana, which lets remember had only been instituted by Emperor Caesar Augustus in the year BC 27?
Christ’s birth was perfectly timed during the middle of the reign of the Empire’s first ruler, a period of unprecedented peace, prosperity and stability for the world of classical antiquity. Is there a significance in this decision other than it being an inscrutable decree of divine providence?
The great Catholic poet Dante Alighieri (famous for his Divine Comedy) had a very ingenious, if controversial, answer to this question in his De Monarchia:
CHAPTER XVI: Christ willed to be born in the fullness of time when Augustus was Monarch
- A phenomenon not to be forgotten attests the truth of all the arguments placed in order above, namely, that condition of mortals which **the Son of God, when about to become man for the salvation of man, either awaited, or ordained at such time as He willed.**1 For if from the fall  of our first parents, at which point of departure began all our error,2 we survey the ordering of men and times, **we shall find no perfect Monarchy, nor the world everywhere at peace, save under the divine Monarch Augustus.3 That  men were then blessed with the tranquillity of universal peace all historians testify, and all illustrious poets; this the writer of the gentleness of Christ4 felt it meet to confirm, and last of all Paul, who called that most happy condition “the fulness of the time.”**5 Verily, time and all temporal things were full, for no ministry to our happiness lacked its minister. But what has been the condition of the world since that day the seamless robe6 first suffered mutilation by the claws of avarice, we can read—would that we could not also see! O human race! what tempests must need toss thee, what treasure be thrown into the sea, what shipwrecks must be endured,7 so long as thou, like a beast of many heads,8 strivest after diverse ends! Thou art  sick in either intellect,9 and sick likewise in thy affection. Thou healest not thy high understanding by argument irrefutable, nor thy lower by the countenance of experience. Nor dost  thou heal thy affection by the sweetness of divine persuasion, when the voice of the Holy Spirit breathes upon thee, “Behold, how good and how pleasant it is for brethren to dwell together in unity!”…
Now Christ willed to be born of a Virgin Mother under an edict of Roman authority, according to the testimony of Luke,9 his scribe, in order that the Son of Man, made man, might be numbered as a man in that unique census. This fulfilled the edict. It were perhaps more reverent to believe that the Divine Will caused the edict to go forth through Caesar, in order that God might number Himself among the society of mortals who had so many ages awaited His coming.10
- So Christ in His action established as just the edict of Augustus, exerciser of Roman authority. Since to decree justly presupposes jurisdictional power, whoever confirms the justice of an edict confirms also the jurisdictional power  whence it issued. Did this power not exist by Right, it would be unjust.
I am curious to hear some thoughts on Dante’s exegesis, in this regard.
He argues that Christ’s birth under Roman sovereignty, during the reign of the first Emperor, essentially legitimated a universal imperium or ‘community of states’ of some sort as being the most desirable international politico-legal order for humankind.
In the medieval period the Church-sponsored “Peace and Truce of God” was explicitly inspired and developed the concept of Pax Romana, albeit in a Christianized form.