At the time when the Virgin Mary gave birth to Jesus, all armed conflicts had ceased on earth. It was the time of the long Pax Romana of Augustus.
The Jews were actually expecting the birth of their mysterious Christ precisely in those years (with calculations based on the prophecy of the 70 septenaries), and this Messiah was expected to be the Prince of Peace. The Talmud explained that he would come when the world had ceased fighting. And this did happen, at the time of the peace of Augustus.
There was a period of 25 years without any wars—an unprecedented pause in all armed conflicts—a period of peace during which the Prince of Peace was indeed born!