Aretas IV was the king of Nabataea, a region just south of Perea that often contended with Herod Antipas' territories. Around AD 27 Antipas married Aretas' daughter, which won Aretas' favor and gave Antipas security, though war always threatened between the two regions. Two years later Antipas fell for his niece Herodias, who agreed to marry him only if he divorced the Nabatean princess. The princess learned of the plan and fled to her father's court. Aretas took severe offense at Antipas' caprice and nursed a grudge against the tetrarch. That grudge bore fruit in AD 36, when Aretas launched a successful invasion of Perea. Emperor Tiberius ordered Vitellius, a Roman general in Syria, to reclaim the region. Vitellius, however, had been slighted when Antipas rushed ahead to Tiberius and took credit for a treaty with Parthia that Vitellius had made, so he was reluctant to help. When Tiberius died the following March, Vitellius abandoned the effort altogether and left Perea occupied. Aretas' invasion was thus the first step in Antipas' downfall, a consequence of his own unfaithfulness and political scheming.