Beware the Ides of March," the soothsayer urges Julius Caesar in Shakespeare's Tragedy of Julius Caesar (act I, scene ii). Despite the forewarning, Caesar is stabbed in the back by his friend Marcus Brutus. Caesar falls and utters his famous last words, "Et tu, Brute?" (And you, Brutus?)
Shakespeare's source for the play was Thomas North's Lives of the Nobel Grecians and Romans, which detailed the murder of Caesar in 44 B.C. Caesar's friends and associates feared his growing power and his recent self-comparison to Alexander the Great and felt he must die for the good of Rome. North's work translated a French version of Plutarch, which itself had been translated from Latin. Shakespeare's version was written about 1599 and performed at the newly built Globe Theater.
Originallly published on History.com