Divorce
Herodias later married Herod II's half-brother, Herod Antipas. According to Josephus:
Herodias took upon her to confound the laws of our country, and divorced herself from her husband while he was alive, and was married to Herod Antipas
According to the Gospel of Matthew and the Gospel of Luke, it was this proposed marriage that John the Baptist opposed. The Gospel of Matthew indicates that John was executed because he criticized this marriage. Josephus does not say this but the two events, the marriage and the execution — and the resulting war with Aretas IV Philopatris, King of the Nabataeans — may be linked.
Herod had lived in Rome with Herodias as a private citizen and therefore survived his father's deathbed purges. Herod Antipas and his other remaining half-brothers shared Judaea out amongst them.
Read more about this topic: Herod II