Trebonius Gaius Trebonius ( c . 92 BC – January 43 BC ) was a military commander and politician of the late Roman Republic , who became Suffect Consul in 45 BC . A trusted associate of Julius Caesar , he was later among those who instigated the plot to assassinate the Dictator . Early career . Born c . 92 BC , Trebonius ' father was an " eques " , but had not been a magistrate , and the son was considered a " Novus Homo " ( " New Man " ) , one of several in Caesar ' s circle . He served as Quaestor around 60 BC , during which he attempted to prevent the adoption of Publius Clodius Pulcher into a plebeian family , against the wishes of the Triumvirs . However , by the time Trebonius was elected Plebeian Tribune in 55 BC , he had become one of their supporters . During that year , Trebonius proposed a " Lex Trebonia " to the Tribal Assembly that the consuls Pompey and Marcus Licinius Crassus receive the provinces of Syria , Hispania Citerior and Hispania Ulterior . Further , that their commands would last for five years , and that the proconsuls would possess the right of making war or peace at their discretion . Cato the Younger , a noted opponent of Pompey , spoke against the bill , attempting to filibuster the motion , causing Trebonius to firstly expel him from the Forum , before ordering him to be taken to prison . However , the large crowd which accompanied Cato caused Trebonius to change his mind and order his release . Eventually the law was passed , with the five - year commands to Pompey , who received the two Spanish provinces , and Marcus Licinius Crassus , who obtained Syria . Caesar ’ s legate . As a reward for his service to the Triumvirs , in 54 BC , he was made one of Julius Caesar ’ s legates , with whom he served for the next five years during Caesar ’ s campaigns in Gaul , with Caesar commenting favourably on his performance during those years . In 54 BC he accompanied Caesar during his second expedition to Britain , where he was placed in charge of three legions who successfully defeated a concerted attack by the forces of Cassivellaunus . Upon Caesar ’ s return to Gaul , Trebonius , along with one legion , was stationed for the winter with the Belgae at Samarobriva . From here he accompanied Caesar in coming to the aid of Quintus Cicero who was besieged during the beginning of Ambiorix ' s revolt against Roman control of Gaul . In 53 BC , Trebonius was given a special command against the Eburones , specifically to harass the area in the vicinity of Huy . After the defeat of Ambiorix , he continued to serve Caesar ; in 50 BC he was placed in charge of the winter quarters in Belgic Gaul , in command of four legions while Caesar was in Ravenna , preparing to confront Pompey and his enemies in the Senate . When Caesar heard that the consul Gaius Claudius Marcellus Minor had asked Pompey to defend the state against Caesar , he ordered Trebonius on October 20 , 50 BC to take three legions and move to Matisco , where he was to wait for further instructions . These arrived in April 49 BC , where Caesar instructed him to travel down to Massilia to take command of three newly recruited legions from Northern Italy and begin the siege of Massilia . Arriving around April 3 , 49 BC , Trebonius began preparing for the siege under Caesar ’ s eye , before leaving Trebonius on April 14 to conduct the land assaults , while Decimus Junius Brutus Albinus command the naval forces . Before he commenced the siege , Trebonius collected labourers and cattle from the Province , ordered timber and wood suitable for wattle - work to be brought up , and then proceeded to construct the principal terrace . The siege lasted from April 19 through to September 6 , as Trebonius erected a contravallation to blockade the town by land . He also constructed terraces to directly assault the walls , and used battering rams and mines to try to breach the walls . Eventually , in early July , Trebonius ’ s men broke through the wall , and the Massilians approached Trebonius and begged him to stop operations until the arrival of Caesar , where they would agree to capitulate to him . Trebonius , after conferring with his fellow officers , agreed to suspend the attack , as Caesar had told him under no circumstances was he to storm the town . This led to his soldiers becoming disgruntled , as they were hoping to sack the town and they blamed Trebonius for halting the attack , and they were only kept under control with great difficulty . Then in late August , Trebonius was surprised when the Massilians burst out of the town , took advantage of the lack of guards posted around , and destroyed the siege equipment which had breached the walls . Trebonius therefore resumed the siege , and proceeded to weaken their defences . The Massilians , hearing word of Caesar ’ s victories in Spain , again offered to surrender , and asked Trebonius to again wait for Caesar . He agreed , although this time he insisted that the defenders should surrender their weapons , their treasure and their ships , thereby bringing the siege to an end . Later career and plotting Caesar ’ s assassination . Following Caesar into Italy , Trebonius was elected Urban Praetor in 48 BC , and was given the task of administering Caesar ’ s debt laws . In this , he had to deal with the ambitions of Marcus Caelius Rufus , the " Praetor peregrinus " , who had turned against Caesar as he had been hoping for the post of Urban Praetor . Caesar ’ s debt laws robbed him of the chance clear his enormous debts , and so he was determined to obstruct Trebonius ’ s administration of the law and to court popularity by siding with the debtors . He set up his chair next to Trebonius and brazenly declared that if anyone felt cheated by Trebonius , he would listen to their case favourably . When no - one took him up on his offer , Rufus proposed instead to cancel all debts , and instigated a mob to attack Trebonius , who drove Trebonius from his tribunal . Trebonius continued to oppose Rufus ’ s debt relief measures , until Rufus fled Rome . During that year , Trebonius also helped Cicero after Cicero ’ s return to Italy . At the end of the year he was given a proconsular command and sent to govern Hispania Ulterior , replacing Quintus Cassius Longinus , who was accused of mismanaging the province He held this position until 46 BC , where he was confronted by rebellious legions , and the resurgence of Pompey ’ s forces . They drove him out of his province by the summer of 46 , with Trebonius returning at the end of the year accompanied by Caesar . It was during this year that Trebonius approached Marcus Antonius , bringing up the notion of a plot to assassinate Caesar . Cicero even claimed , years later , that Trebonius and Marcus Antonius conspired to send an assassin to murder Caesar in 45 BC . Caesar appointed Trebonius Suffect Consul on 1 October 45 BC , with Trebonius actively continuing to plot against him . According to Cicero , Trebonius preferred the liberty of the Roman people over his friendship for Caesar . In early 44 BC , he dared to protest to Caesar for Caesar ’ s refusal to stand when the members of the Senate came to inform him of the honors the Senate had conferred upon him ; Caesar apparently simply stared back at him arrogantly without making a comment . On March 15 , 44 BC , on the day marked for the Dictator ’ s assassination , Trebonius was the person who kept Mark Antony outside the Senate while Caesar was being stabbed . Having been nominated by Caesar for the post of Proconsul for Asia , he immediately left for the province during 44 BC . While there , he raised money and troops for Brutus and Cassius . He also helped Cassius on his way to Syria later in the year . Later , he attempted to fast track Publius Cornelius Dolabella in his passage through Asia by providing whatever supplies he needed , as well as refusing to open cities for Dolabella . However , Dolabella took Smyrna in Asia Minor , where he captured Trebonius in the process . In January 43 BC , Dolabella put Trebonius on trial for treason before proceeding to torture him and finally killing Trebonius by beheading him .