Vitellius was now sole ruler in the Roman world. However, he had taken a large army with him to Italy, and had left behind only a quarter of the legionaries. The Rhine was virtually unguarded. Almost immediately after he had occupied Rome, he sent back military units. Among these were eight auxiliary units of Batavian infantry which had fought bravely on the Po plains. They had already reached Mogontiacum (modern Mainz) when they received orders to return to Italy. Again, they had to assist Vitellius, this time in his struggle against a new pretender, the commander of the Roman forces in Judaea, Titus Flavius Vespasianus, better known as Vespasian. After Galba, Vitellius, and Otho, he was the fourth emperor of the long but single year 69.