What did ancient heralds do before an emperor arrived?

Les explains that in ancient history a herald would come perhaps a day or two before a great emperor or the leader of an empire. He would begin at one end of a city and, like a trumpet, announce the coming of his emperor. He would never go back and retrace his steps. He would announce it once as he went through the city, and that was it—a one-time heralding. Les connects this to John the Baptist, who was a herald, an announcer of the king. He also notes that some have made a connection here to how the church has lost sight of propagating the gospel, since many mission boards decry that 90 percent of God's servants proclaim the Word to only 6 percent of the world's people, while most Christian workers labor in America.