Gaius Antonius Hybrida

In 87 BC, Hybrida accompanied Lucius Cornelius Sulla on his campaign against Mithridates VI of Pontus either as a military tribune or as a legatus.[3][8] Two years prior, the Mithridatic Wars had begun due to a dispute between Mithridates and Nicomedes III of Bithynia over the Roman province of Cappadocia. Mithridates invaded and conquered both Bithynia and Cappadocia before moving on to invade the Roman province of Asia,[9] where he massacred all the Roman citizens he could find.[10] He then sent troops to invade Greece, which in turn spurred some of the city-states to rebel against Rome.[11] At the time Rome was embroiled in internal conflict through the Social War from 91 to 87 and then almost immediately after, a disturbance occurred in Rome which further delayed Sulla's response to Mithridates.[11] After this was dealt with, Sulla, accompanied by Hybrida, marched on Greece to face the Mithridatic-Greek armies under the command of Archelaus and Aristion.[3][11] The First Mithridatic War continued from 86 to 83.[3][11] During this campaign, Sulla drove the Mithridatic-Greek armies back towards Athens and besieged them there. After capturing Athens, Sulla marched north and defeated two large Mithridatic armies at Chaeronea and Orchomenus. He invaded Asia Minor the following year and then successfully forced a peace with Mithridates in 83.[11] Sulla returned to Italia in 83, leaving Lucullus to command forces in Asia and Hybrida to command a small cavalry force in Achaia.[3][11] In Achaia, Hybrida levied contributions on the province, an offence for which he was prosecuted by the young Julius Caesar in 76. However, he refused to appear and succeeded in escaping punishment after appealing to the people's tribunes.[3][8][12]

Years later, in 70 BC, the censors Gellius and Lentulus expelled Hybrida from the Senate for the criminal offences committed by him while in Greece, for disobeying the summons of a praetor[lower-alpha 3] and for the wasteful use of his property.[3] Hybrida is described by the English Historian Antony Kamm as "a thoroughly disreputable character" and by author Dunstan as "thuggish". In spite of this notorious reputation, Hybrida regained his seat in 68 or 66 after being elected as praetor.[13] Hybrida also probably served as a tribune sometime before his expulsion from the Senate and also served as aedile[lower-alpha 4] from 69 to 66.[3] For the consular elections of 64, Hybrida and another candidate, Catiline, received the support of Caesar and Marcus Licinius Crassus for their bids to become consuls of Rome. Dunstan describes Catiline as an "opportunist" who had gained notoriety for murders during Sulla's proscriptions; Kamm expands on this description by including the alleged murder of his own son, violation of a Vestal Virgin and many other "unspeakable profligacies".[13][14] A third candidate also existed for the consular elections, Marcus Tullius Cicero, whom Dunstan describes as being a "brilliant orator", but he came from an undistinguished family.[14] In the end, Cicero and Hybrida were elected to the position of consul for the year 63.[13][15]

Catiline was once again a candidate for the consulship for the year of 62 BC.[16][17] As part of his campaign, Catiline promised reforms to reduce and cancel debts, a proposal which brought him the support of bankrupt aristocrats, debtors, and poor farmers whose agricultural ventures had failed.[16][17] This proposal, however, also pitched the conservatives, moderates and members of the Senate against him.[16][17] On the day of the elections, Cicero attended wearing a breastplate under his tunic in an attempt to raise the alarm in the Senate and provoke the fear that Catiline might resort to violence as consul.[16][17] In the end, Lucius Licinius Murena and Decimus Junius Silanus were elected to the position of consul and Catiline's bid for the position had once again failed.[16][17] In response, and having lost hope of having a successful political career, Catiline began to conspire against the Senate.[16][17] Cicero employed spies to keep tabs on Catiline and began to piece together a case against Catiline to be brought to the Senate.[16][17] In the midst of these developments, Hybrida first tried to remain on the fence, but was forced to action in the face of the risk of having himself charged as a co-conspirator.[6] On 6 November 63, Cicero learned of a plot to have himself and other members of the Senate assassinated and Rome set on fire and sacked.[17] While this was happening, Catiline and an army of his supporters, under the command of Gaius Manlius, were to march on Rome and take control of the city.[17] In response to these allegations, Cicero called a meeting of the Senate which Catiline himself attended.[17] At this meeting, Cicero launched an attack against Catiline denouncing him "to his face" while providing the details of the plot that he had learned of the night before.[16][17] After this meeting, Catiline fled the city of Rome to join up with Manlius and an army of approximately 10,000 men at Etruria.[16][17] The Senate, upon becoming aware of this, issued a senatus consultum ultimum declaring Catiline and his army as enemies of the state.[16][17] Finally, Cicero arrested five men to be brought to the Senate for an immediate trial, the outcome of which was an order for their executions which was delivered and enacted by the Senate.[18]

Towards the end of 63, Hybrida went to Etruria to assist the praetor Quintus Metellus Celer in preventing Catiline escaping through the Alps and into Gaul.[3] Catiline, hoping that Hybrida might choose to help him, opted to engage him and his consular army rather than the forces under the praetor.[3] Hybrida, however, had given command of the army to his legate, Marcus Petreius, having either suffered a bout of gout or pretended to have.[3][6] Catiline put up his final resistance in Pistoria, Etruria, with an army of 3000 men.[6] Here, Petreius and his soldiers massacred the entire army, killed and beheaded Catiline, and then sent his head to Rome.[6] Hybrida, having adhered to the agreement that he had with Cicero and the Senate, was granted the governorship of Macedonia at the end of his consulship.[3]