Claudius Silvanus Claudius Silvanus ( died 7 September 355 ) was a Roman general of Frankish descent , usurper in Gaul against Emperor Constantius II for 28 days in AD 355 . Origin and career . Silvanus was born in Gaul , the son of Bonitus , a Laeti c Frankish general who had supported Constantine I in the civil war against Licinius . Like so many other Franks of his times , and like his father before him , he was a loyal and thoroughly romanized " barbarian " in the military service of the Empire . By AD 351 , he held the rank of tribune and was one of the senior officers who defected to Emperor Constantius II at the Battle of Mursa Major , after initially supporting the usurper Magnentius . An able soldier , Silvanus was eventually promoted to the rank of Magister militum per Gallias , a crucial post in the West . About AD 352 - 353 Constantius personally entrusted him with the difficult task of driving the Alamanni tribesmen raiding and looting in Gaul back beyond the Rhine , and restoring the fast eroding Roman authority in the province . This Silvanus fulfilled partly by bribing the Alamanni chieftains with the taxes he had collected , partly by defeating the Alamanni in battle and partly by suppressing the local bagaudae insurrections flaring up again in central and northern Gaul . Trial and usurpation . The corrupt " coterie " of Constantius II managed to persuade the suspicious , paranoid emperor , that Silvanus was planning to seize power . According to Ammianus , the praetorian prefect Lampadius and the ex - treasurer of the privy purse , Eusebius , used a sponge to alter a letter sent by Silvanus to his friends in Rome . The altered letter suggested that Silvanus was attempting to win support within the Senate for a coup . Constantius ' court clique , with the exception of fellow Frankish generals Malarich and Mallobaudes , was uniformly against Silvanus . Courtiers Apodemius and Dynamius forged further correspondence that cast doubt on Silvanus ' loyalty . Constantius then held a trial where Silvanus ' allies were successful in defeating the spurious charges against the general . But Silvanus , unaware of the success of his supporters , responded to the threat of condemnation and execution by actually proclaiming himself emperor on 11 August 355 in Colonia Agrippina ( modern Cologne ) . Late Roman historian Michael Kulikowski has argued that the entire episode was a later invention , created as an excuse to rid Constantius II of Silvanus before he became a threat . His primary basis of this argument is the fact that no coins minted with Silvanus ' image have been found to date , since virtually every usurper minted coins as an attempt to legitimize his authority . Death of Silvanus . Constantius II , who was staying in Milan , ordered Silvanus to present himself at court , then sent his trusted " magister equitum " Ursicinus to take over Silvanus ' post . Ursicinus was himself at odds with Constantius ' clique , and Silvanus no doubt trusted the veteran general . The letter that Ursicinus gave to Silvanus did not indicate that Constantius already knew of Silvanus ' bid for power , so Silvanus considered himself safe . However it seems that Ursicinus betrayed and then arranged for the murder of Silvanus by co - opting some of the rebel soldiery . These men killed the usurper ' s guards and dragged Silvanus from the Christian church where he was worshipping then hacked him to death with their weapons . Ammianus ' s report of Silvanus ' s death . It has been suggested by at least one scholar that Ammianus invented the entire coup attempt to gloss over the role played by his patron , Ursicinus , in the murder of a fellow general . This theory suggests that Constantius had grown suspicious of the popular Frankish general and so offered his post to Ursicinus , who then murdered his peer in the course of a botched change of command . It has been noted that Silvanus did not mint any coinage ( which would have been a clear indication of a usurpation attempt ) , unlike other equally - short lived usurpers of the era , such as Poemenius . However , the thesis of a concocted coup attempt is generally rejected by scholars . The lack of numismatic evidence is not determinative , because Trier , the nearest minting centre to Colonia Agrippina , closed its gates to Silvanus . Ammianus thus concludes his treatment of the Silvanus episode : " Such was the end of a commander of no small merit , who was driven by fear of the slanders in which a hostile clique had ensnared him in his absence to adopt extreme measures in self - defence " ( 15 . 5 . 29 ) .