New Defender's Study Bible Notes
12:1 Herod the king. King Herod, as described in this chapter, was Herod Agrippa I, grandson of Herod the Great, the cruel king who slaughtered the babies at Bethlehem (Matthew 2:1,16), and the father of Herod Agrippa II, who in turn was the King Agrippa who later tried Paul (Acts 25:13–26:32). Another Herod, Herod Antipas, was one of the sons of Herod the Great, and he was tetrarch of Galilee during the ministries of John the Baptist and Jesus. Another son of Herod the Great, Aristobulus, was the father of Herod Agrippa I, the Herod who had James executed.
12:2 James. It is interesting that James, son of Zebedee, was the first of the apostles to be martyred, whereas John, his brother, survived all the rest, writing the last book of the Bible while imprisoned on the Isle of Patmos.