The Book of Zechariah expands upon Ezekiel's New Jerusalem. After the Second Temple was built after the exile, Jerusalem's population was only a few hundred. There were no defensive city walls until 445 BCE. In the passage, the author writes about a city wall of fire to protect the enormous population. This text demonstrates the beginning of a progression of New Jerusalem thought. In Ezekiel, the focus is primarily on the human act of Temple construction. In Zechariah, the focus shifts to God's intercession in the founding of New Jerusalem.