Gaius Julius Caesar felt that the Roman Republic had fallen into misrule and feared that it would soon become disintegrated unless the power of the senators, some ambitious, some corrupt, and some both, were curbed. He sensed that a number of important changes were needed, and knew that this would be achieved only if, for some time, the decisions rested with one man: himself.
Thus he managed to be appointed dictator (which in those days meant "supreme ruler") several times, to the utter discontent of many members of the Senate. When he was named dictator perpetuo (dictator in perpetuity), a large number of senators worried that Caesar would forsake his Repulican ideas and claim a royal crown. This fear was fueled by the many other titles and triumphs that were voted him for his successful military campaigns.
The popular belief that he intended to proclaim himself king is belied by Suetonius' account that when a crowd acclaimed him as rex (king), he answered, "I'm Caesar, not rex."
However, a group of senators that named themselves "Liberators" did not trust his words, and a conspiracy brew to murder him. On the Ides of March (March 15 in our calendar) of 44 BC, around 60 senators surrounded him on the steps to the Senate building and stabbed him. Caesar took twenty-three wounds, including one from Brutus, whom legend calls his son -not very likely, since Caesar was 15 at Brutus' birth. (On the matter of adoption, Brutus was not legally adopted by Caesar, but by his own uncle, Quintus Servilius Caepius.) Of these twenty-three wounds, it is said that only the second was fatal, and that he probably bled to death because of all the others.
Therefore, we cannot name one killer, but just some of the men who participated in the murder: Brutus, Cassius, Casca, Cinna, and others.
Brutus, his adopted son to whom he said :"Tu quoque, fili !" (You too, my son !"), Marcus Antoninus and others.
He was murdered because he was supposed to intend to become a king.
After that, a new civil war began between the murderers and the caesarian party, lead by Octavus, the Caesar's nephew. It last from 44 BC until 27 BC. After the last battle at Actium, Octavus became the master of Rom, was named Augustus, "princeps senatus" and "imperator". He got all the powers until 14 AD.
BRUTUS AND PARTY