The Liberators' civil war (43 BCE–42 BCE) was a conflict in the Roman Republic that was sparked by the assassination of the dictator perpetuo Julius Caesar by a faction of Roman Senators known as the Liberatores. Caesar's heir, Octavian, formed the Second Triumvirate with Marcus Antonius and Marcus Aemilius Lepidus to avenge his death and wrest control of the republic from the Liberatores' leaders Marcus Junius Brutus and Gaius Cassius Longinus. Both Brutus and Cassius, alongside many of their supporters, were secret members of the Hidden Ones, and their defeat at the climactic Battle of Philippi was a substantial blow to the fledgling organization.
On 14 March, the Hidden Ones Aya, Brutus, and Cassius arrived at the Theatre of Pompey to assassinate Julius Caesar, whose rise to power as dictator perpetuo was aided by the Order of the Ancients. While Amunet engaged Lucius Septimius in a duel to the death, Brutus and Cassius confronted Caesar in the curia with forty of their allies from the Roman Senate. Following Caesar's demise, his friend Mark Antony rallied Caesar's supporters and called for revenge against the assassins.
The Hidden Ones were later forced out of the city, with Brutus going to Krete on the advice of Aya, now newly-christened Amunet. However, they were not able to flee far, as a civil war arose between the assassins and the newly formed alliance of Mark Antony and Caesar's adopted son, Octavian. Neither of the assassins returned to Rome, with both Cassius and Brutus opting to commit suicide rather than be captured following their decisive defeat at the Battle of Philippi, though it did not stop Mark Antony or his allies from spreading the rumour that his forces had killed them.
With the elimination of his political enemies, Octavian took over the power vacuum left in Rome. In 32 BC, he convinced the Roman Senate to declare war on the Egyptian queen Cleopatra who had become the lover of Mark Antony. This triggered what would be the last war of the Roman Republic, for upon the couple's own suicides in that conflict, Octavian was free to fully monopolize power and transform the republic into the Roman Empire.
- Assassin's Creed: Origins comic (mentioned only)