PREVIOUSLY IN BETHLEHEM...
In order to fix such a mess and to bring the presence of God back into the midst of His chosen people, you have to understand the back story. In the world of drama, every character in a play, or in a television show or movie, has a back story. This is what happened before they came on the scene in the movie.
Most movies or plays or television shows are what is called "slice of life." You jump into action that is already underway. During the early part of the show, the writers reveal to us, the audience, what was going on before. Some television show jumpstart this exercise by commencing the show with a brief synopsis of what happened over the course of the last couple of episodes. They always preface it with the familiar phrase, "Previously on _________."
The back story of Jesus' birth was Chapter 1 of Luke. The end of the back story begins in Chapter 2, verse 1: "In those days Caesar Augustus issued a decree that a census should be taken of the entire Roman world. And everyone went to his own town to register." (2:1,3)