Luke tells his reader in Acts 1-1-3, Theophilus, that he writes to give certainty to the truth of Jesus Christ, the Church, and the trajectory of world history. How critical at a time when the Church was expanding, but no where safe---All Luke records has the successful mission of Christ-the victory of Christ-as his thesis. Acts 12 is no exception. Here, Luke shows that, where Old Israel failed under similar circumstances, the Church-as the true and faithful Israel-will succeed. --Prayer is the hinge of the passage, though it's only mentioned in 2 of the 25 verses. Why does prayer make the church victorious here-