In this moment of crisis, Herod looked to the Romans for help. He fled Jerusalem with his family under cover of darkness, and after defeating the Parthians and their Jewish allies in a desperate battle at the site where he would later build Herodium, he traveled on to Rome, where the senate, remembering his unswerving loyalty, named him King of Judaea. He walked out of the senate building arm in arm with the two most powerful men in the Roman world: Mark Antony, the soldier and orator who ruled the Roman east, and Octavian, the young patrician who ruled the west, and who, nine years later, would defeat Antony and assume command of the entire empire, subsequently taking the title "Augustus." Then, in an act that symbolized the many accommodations he would have to make to keep his slippery grip on power, Herod led the procession up the Capitoline Hill to the Temple of Jove, Rome's most sacred shrine, and there the King of Judaea offered sacrifice to the gods of pagan Rome.
Now Herod had his kingdom, but he still had to conquer it, which took three years of hard fighting. Finally, in 37 B.C., he captured Jerusalem, and Judaea was his—at least politically. To bolster his social and religious authority, he divorced his first wife, Doris, and married Mariamne, a Hasmonaean princess. But the Hasmonaean threat remained. Two years later, at Passover, Mariamne's teenage brother, the high priest in the Second Temple, received a warm ovation from the crowds of worshippers; Herod, fearing that the young man might one day usurp his throne, had him drowned in a swimming pool in his palace in Jericho.
The Hasmonaeans were not his only concern. From 42 to 31 B.C., while Mark Antony ruled the Roman east, Herod remained his staunch friend and ally, despite the ambitions of Antony's beautiful Egyptian queen, Cleopatra, who persuaded her love-struck husband to carve out choice portions of Herod's kingdom for her, and even tried to seduce Herod. (He declined her advances.) In 31 B.C., the political landscape was transformed by the Battle of Actium, during which Octavian crushed the combined armies of Antony and Cleopatra and became the first emperor of Rome. Herod, knowing that Octavian would take a dim view of his long-standing friendship with Antony, rushed to the island of Rhodes to meet the emperor and presented himself without his crown, but with all of his kingly dignity. Instead of downplaying his devotion to Antony, he underscored it and promised to serve his new master, Octavian, with the same loyalty in the future. Octavian was so impressed by Herod's frankness and poise that he confirmed him as King of Judaea, and later added other territories to his realm, saying that Herod's megalopsychia—his greatness of spirit—was too large to fit a small kingdom like Judaea.