Characters refer to anyone from the poorer classes as "plebs". While in earlier centuries the plebeians generally did constitute a politically disenfranchised and poorer class, by the time the show takes place the two groups had more or less formal political equality and there were enough instances of plebeians becoming rich and patricians becoming destitute that the terms had little bearing on economic status. With the era's conflicts being mostly rich vs. poor, depicting the rivalry as essentially plebeian vs patrician is very attractive but also very inaccurate since many top optimates (most notably Pompey and Cicero) were in fact very wealthy plebeians. The show does show that the Tribune of the Plebs had a veto over the Senate and that Pompey is a republican plebeian while Caesar is a populist patrician, but doesn't allow such facts to detract from its patrician vs. plebeian themes.
Atia is disdainful of the plebs despite the fact that her real life husband Gaius Octavius was from a plebeian family, and she calls Pompey "a villainous little pleb" even though he's her dad's cousin.
Agrippa's angst about his supposed lower-class background and it's specific citation in the Star-Crossed Lovers angle of his relationship with Octavia in "Philippi" are undermined by the historical fact that he ultimately married Octavian's daughter Julia.
In Season 1, Atia mistakenly concludes her son Octavian has had a sexual encounter with her uncle Gaius Julius Caesar and applauds Octavian for the political influence this will give them, which is played for the Deliberate Values Dissonance of her approving of pederasty. However, while it was indeed acceptable for Roman men to have sex with other men or even boys, this was only as long as their partners were not other freeborn citizens. A freeborn male, if proven to have "served" another man sexually (i.e. bottoming or giving fellatio) could lose his political and civil rights and gain the status of "infamy", just like prostitutes, actors, and non-slave gladiators (all of whom were assumed to sell sex at least on the side). And as the younger partner, Octavian would automatically be assumed to have bottomed.note This is actually were we get the rumors that Julius Caesar was bisexual: At 19, he spent some time as a sort of ambassador to a foreign king's court, and there were rumors of them having an affair. As the younger, lower-ranking partner, Caesar would've had no legal defense if his political enemies had ever managed to make the rumours stick and taken him to court over the matter. Hence the smear-campaign of "Caesar is a man to any woman, and a woman to any man." Not only would Atia have never risked her son's future like that but since Octavian was still a minor, any adult man who seduced him would be treated just as if he had raped him: with the death penalty (since it was thought that such a seduction would "corrupt" the future citizen into wanting to serve men sexually for the rest of his life). Not to mention that incest was just as taboo to the Romans as most cultures.
Bodyguards and slaves throughout the series can be spotted wearing the bronze 'heart protector' breastplates worn by Roman soldiers in the early Republic, which by the time the series takes place would be around 300 years out of date.
The series follows a common historical convention by referring to Gaius Octavius as "Octavian" and (less conventionally) "Gaius Octavian Caesar" following his uncle's death. Historically, Octavius called himself "Gaius Julius Caesar" after his uncle's death and "Octavian(us)" was the Insistent Terminology used by Cicero and others to emphasize Octavius' plebeian heritage since he should've called himself "Gaius Julius Caesar Octavianus" to reflect his adopted status.
Caesar inducts a group of bearded Gaulish tribesmen into the Senate, to the outrage of the Senators. In reality, Caesar granted full citizenship to the already heavily-Romanized Cisalpine Gaul (modern northern Italy), which had been a Roman province for over 100 years. The men he admitted to the Senate would have been the wealthy and educated elite of the province and indistinguishable from other Romans (Livy, Catullus and Virgil, amongst others, were natives of the region).
The Gallic forces in the opening battle sequence of the first episode are equipped like a bizarre fusion of fantasy barbarians and bronze age Celts and charge wildly at the Roman lines in a disorganized rabble. In reality, the Gauls would have been equipped with different (and less outrageous) gear and fought in a standard massed formation.
In the aftermath of this sequence, Vercingetorix is shown wielding something that looks suspiciously like a medieval arming sword.
The "blue Spaniards" that Pompey enlists to steal Caesar's eagle are rather based on "Blue Britons", who painted their bodies with woad and fought naked (as written by Julius Caesar himself among others).
Vorenus is called a "First Spear Centurion" when "front line" is probably a better translation of primus pilus. Later, Antony also offers him promotion to "Prefect, of the first grade" when historically prefects (roughly equivalent to a Lieutenant Colonel) were defined by their duties (camp commandant, chief of engineers, chief of cavalry, etc) rather than any grade.
At Caesar's triumph, several signiferes can be seen carrying standards in the shape of dragons. Known as the Draco, this kind of standard was known to the Romans as being used by Dacians and Scythians, but they would not adopt it themselves until the latter half of the 3rd century, around three hundred years after the series takes place.
The show's version of the Battle of Philippi is accurate only in Broad Strokes.
Historically, the battle was so large that it was effectively two simultaneous battles: one between Antony and Cassius and one between Octavius and Brutus. In the series, it's just one big melee.
The series portrays Cassius as dying of battle wounds whereas the real Cassius committed suicide after being defeated by Mark Antony and mistakenly concluding that Brutus had also been defeated by Octavius.
Titus Pullo and Lucius Vorenus were both real men who fought for Caesar in Gaul and their introduction is very loosely based on their brief mention in Caesar's commentary. However, everything else about them is not only fictional but contrary to history. They probably served in the XI Legion rather than the XIII, they saved each other in a skirmish with the Nervii rather than at Alesia, and the real Pullo was a rival centurion rather than an insubordinate legionary and is known to have later fought on Pompey's side at Pharsalus.
Atia's depiction as a Vicariously AmbitiousSmug Snake who loves Mark Antony actually bears far more resemblance to Antony's Adapted Out wife Fulvia than the historical Atia Balba, who was by all accounts a pious matron who was Happily Married to the milquetoast Lucius Marcius Philippus during the show's time-frame. She also lives to see her son become Emperor (in 27 BC) when in real life she died much earlier, around the start of the Second Triumvirate (in 43 BC).
While Cato's personality is pretty accurate, in the show he's the eldest optimate, when in reality he was in the middle: born in 95 BC he was a decade younger than Pompey and Cicero (born 106 BC) and a decade older than Brutus and Cassius (born 85 BC). This has the effect of making him seem more like a Grumpy Old Man traditionalist rather than the radical Good Old Ways reformer he actually was.
Historically, Brutus was estranged from his mother by his decision to divorce his first wife and marry Cato's daughter Porcia (Adapted Out), who was the only woman privy to Caesar's assassination. In the series, Brutus is unmarried and urged into the assassination by Servilia because Caesar spurned her.
There was no historical Quintus Valerius Pompey. The character seems to be a Composite Character of Pompey's sons Gnaeus and Sextus, but it's hard to say since neither Gnaeus' Last Stand at the Battle of Munda or Sextus' Sicilian Revolt were included in the series.
Antony's decision to retain the seemingly incompetent Lepidus seems strange. But in history, they knew each other prior to their first meeting when they were two of Julius Caesar's most trusted lieutenants. It's still unknown whether Lepidus and Mark Antony had already agreed to merge their two forces prior to Lepidus receiving his orders from the Senate.
The Capitoline treasury really did fall into Caesar's hands and prove crucial to his war effort. However, historically Caesar got it not through any fateful foiling of Pompey's attempts to remove it but by having his men blatantly and sacrilegiously batter down the temple doors and loot the place.
In Season 2, Octavian is living in Rome with his mother and gives Antony his strategy to out-maneuver Brutus and the assassins. Historically, Octavian was effectively off at college in modern-day Albania when Caesar was assassinated and played no role in the immediate aftermath, only arriving two months later after appropriating millions of sesterces and winning over Caesar's veterans in southern Italy.
In Season 2, Cleopatra travels to Rome to appeal to Antony and Octavian to endorse her son Caesarion's claim to the (nonexistent) throne. In reality, Cleopatra was actually living in Rome at the time of Caesar's assassination and immediately fled for her life (and that of her son) since both Antony and Octavian were clearly laying claim to Caesar's mantle themselves and would not have hesitated to immediately kill a third rival successor. It was only once she'd set herself up as an indispensable ally to Antony that she began pressing Caesarion's claims.
Caesarion's fate is also as an example, in the show he secretly survives and lives with Titus Pullo, whereas in real life he really was killed on Octavian's orders.
In the series, Cicero's hands are nailed to the Senate door. Historically, his hands and tongue were nailed to the rostrum, the large speaker's platform near the Forum.
Eirene is pregnant for just three episodes, but these episodes cover four years of historical events between the Battle of Philippi (42 BC) and the betrothal of Octavian and Livia (38 BC).