Julius Caesar straddles two important dramatic genres: tragedy, of course, as well as history. Though Shakespeare in no way intended the play to be historically accurate, he did consult a number of historical sources that lend the play some historical credence. His primary source was Plutarch's The Lives of the Noble Greeks and Romans, translated by Thomas North (this was also his primary source material for his later play, Antony and Cleopatra). From this text, Shakespeare pulled a number of important details about Caesar, Brutus, and Antony (Antonius).
Shakespeare also made minor use of other texts, including The Twelve Caesars. This text, written by the Roman historian Suetonius, is composed of biographies of Julius Caesar and the first eleven emperors of Rome. It is from this text that Shakespeare appears to have pulled the famous line, "et tu, Brute?" ("you too, Brutus?") that Caesar utters just before his death.
The title of the play itself is The Tragedy of Julius Caesar, which shows Shakespeare's intention to keep the play out of the discourse of history. Indeed, Shakespeare's history plays are almost all histories not of Rome but of England, detailing the reigns a number of English kings. Julius Caesar, by contrast, makes use of a number of dramatic devices more closely associated with tragedy – namely supernatural occurrences and the rise-and-fall trajectory of its hero. But perhaps the most convincing reason why Julius Caesar was written as a tragedy has to do with English politics: Rome was a controversial topic for writers at the time, as Roman political ideology, or republicanism, posed a threat to the endurance of the English monarchy. By crafting the play as a tragedy rather than a history, Shakespeare avoided the direct historical comparison between Rome and England at the same time the content of the play makes such a comparison difficult to ignore.
