Julius Caesar, the Roman dictator, was assassinated by a group of senators on the Ides of March (15 March) of 44 BC during a meeting of the Senate at the Theatre of Pompey in Rome. The senators stabbed Caesar 23 times. The senators claimed to be acting over fears that Caesar's unprecedented concentration of power during his dictatorship was undermining the Roman Republic, and presented the deed as an act of tyrannicide. This was the act that also condemned both Cassius and Brutus to the Ninth Circle of Hell where they would be eternally gnawed and chewed on by Satan.
At least 60 senators were party to the conspiracy, led by Marcus Brutus, Gaius Cassius and Decimus Brutus. Despite the death of Caesar, the conspirators were unable to restore the institutions of the Republic. The ramifications of the assassination led to the Liberators' civil war and ultimately to the Principate period of the Roman Empire.
Caesar had served the Republic for eight years in the Gallic Wars, fully conquering the region of Gaul. After the Roman Senate demanded Caesar to disband his army and return home as a civilian, he refused, crossing the Rubicon with his army and plunging Rome into Caesar's Civil War in 49 BC. After defeating the last of the opposition, Caesar was appointed dictator perpetuo ("dictator in perpetuity") in early 44 BC. Roman historian Titus Livius describes three incidents that occurred from 45 to 44 BC as the final causes of Caesar's assassination — the "three last straws" as far as some Romans were concerned.
The first incident took place in December 45 BC or possibly early 44 BC. According to Roman historian Cassius Dio, after the Senate had voted to bestow a large group of honors upon Caesar, they decided to present them to him formally, and marched as a senatorial delegation to the Temple of Venus Genetrix. When they arrived, etiquette called for Caesar to stand up to greet the senators, but he did not rise. He also joked about their news, saying that his honors needed to be cut back instead of increased. Roman historian Suetonius wrote (almost 150 years later) that Caesar failed to rise in the temple, either because he was restrained by the consul Lucius Cornelius Balbus or that he balked at the suggestion he should rise. Regardless of the reasoning, by practically rejecting a senatorial gift and not acknowledging the delegation's presence with proper etiquette, Caesar gave the strong impression that he no longer cared about the Senate.
The second incident occurred in 44 BC. One day in January, the tribunes Gaius Epidius Marullus and Lucius Caesetius Flavus discovered a diadem on the head of the statue of Caesar on the Rostra in the Roman Forum. According to Suetonius, the tribunes ordered that the wreath be removed as it was a symbol of Jupiter and royalty. Nobody knew who had placed the diadem, but Caesar suspected that the tribunes had arranged for it to appear so that they could have the honour of removing it. Matters escalated shortly after on the 26th, when Caesar was riding on horseback to Rome on the Appian Way. A few members of the crowd greeted him as rex ("king"), to which Caesar replied, "I am Caesar, not Rex" ("Non sum Rex, sed Caesar"). This was a piece of Latin wordplay; since "Rex" was a family name as well as a royal title, Caesar was suggesting that the crowd was merely shouting the wrong name. Marullus and Flavus, the aforementioned tribunes, were not amused, and ordered the man who first cried "Rex" arrested. In a later senate meeting, Caesar accused the tribunes of attempting to create opposition to him, and had them removed from office and membership in the Senate. The Roman plebs took their tribunes seriously as the representatives of the common people; Caesar's actions against the tribunes put him on the wrong side of public opinion.
The third incident took place at the festival of the Lupercalia, on the 15th of February, 44 BC. Mark Antony, who had been elected co-consul with Caesar, climbed onto the Rostra and placed a diadem on Caesar's head, saying "The People give this to you through me." While a few members of the crowd applauded, most responded with silence. Caesar removed the diadem from his head; Antony again placed it on him, only to get the same response from the crowd. Finally, Caesar put it aside to use as a sacrifice to Jupiter Optimus Maximus. "Jupiter alone of the Romans is king," Caesar said, which received an enthusiastic response from the crowd. At the time, many believed that Caesar's rejection of the diadem was a way for him to see if there was enough support for him to become king, and despised him for it.
According to Suetonius, Caesar's assassination ultimately occurred primarily due to concerns that he wished to crown himself the king of Rome. These concerns were exacerbated by the "three last straws" of 45 and 44 BC. In just a few months, Caesar had disrespected the Senate, removed People's Tribunes, and toyed with monarchy. By February, the conspiracy that caused his assassination was being born.