In his Epitaphios for the emperor Julian, composed in Antioch at some point between 365 and 368, Libanius describes an embezzlement trial that was held most likely in 359, in which Julian ruled against the accused, defying the wishes of Constantius II’s praetorian prefect, Florentius. Libanius puzzlingly suggests that the trial prompted Julian’s campaign to rebuild fortresses in Batavia and to restore shipments of British grain blockaded by barbarian forces. Scholars have yet to explain the causal and chronological relationship between these events. This article suggests that Libanius’s narrative is a propagandistic representation of several distinct stages of the taxation dispute Julian fought with Florentius. With the aid of recent advances in our archaeological understanding of agricultural practices in Britain and on the lower Rhine, the article argues that in response to this dispute, Julian’s Batavian campaign was intended to disrupt longstanding access by barbarians on the lower Rhine to the later Empire’s military supply mechanisms.