Valentinian II
The controversy involving Arbogast began during the regency of Valentinian II, who soon after his recognition as Emperor by Theodosius I became a figurehead for the wiles and ambitions of Arbogast. After being proclaimed as the only "Magister Militum in Praesenti", or commander of the armies in attendance on the emperor in the Western Empire by Theodosius I, Arbogast's authority throughout the Western Provinces, mainly Gaul, Spain and Britain, seemed to be absolute, with him answering only to Theodosius I himself. However, Arbogast was unable to claim control over those territories under his own name and had to do so in the name of Valentinian II instead because he was a barbarian by birth. By 391, Valentinian II had already been isolated in Vienne, his status essentially reduced to that of a private citizen, and the control of the Western armies now belonged to Frankish mercenaries loyal to Arbogast. Furthermore, Valentinian's Court was also overrun by those loyal to Arbogast after Arbogast placed them in favorable positions. During this period, Arbogast became increasingly violent towards Valentinian II and his councilors, so much so, in fact, that Arbogast is described as killing the councilor Harmonius, a friend of the Emperor who had been accused of taking bribes, at the feet of Valentinian II in 391. At this point, Valentinian II began recognizing the extent to which Arbogast's authority had reached, and with Arbogast seemingly expressing his authority over him at will, Valentinian II began sending secret messages to both Theodosius I and Ambrose, Bishop of Milan, pleading for them to come to his aid, even so much as asking Ambrose for a baptism in fear that his death might come sooner than expected at the hands of Arbogast.