Cicero was a famous Roman writer and orator. He lived during the same time as Julius Caesar. Cicero and Julius Caesar did know each other. Both were popular and powerful politicians. Both were successful generals. Both had served as elected Consul, which was the most powerful position in the Republic of Rome's government. Cicero was also a very talented author. He left many of his speeches written down, and others copied them, so we still have them today.
And like Julius Caesar, people came to hear Cicero speak. He was a powerful orator. When Cicero spoke about how people should govern themselves they listened. Julius Caesar knew if anyone could stop him from taking over the government of Rome it would be Cicero.
When Cicero spoke out about government, people listened. Cicero said: "In a kingdom, only the king has many rights. Kings can be wise and just. But rule by one person can easily become tyranny."
Cicero spoke out against Julius Caesar when Caesar declared himself dictator. Because he spoke out, Julius Caesar sent soldiers to arrest him. By then, Caesar had the Roman legion under his control. Cicero had to flee Rome. When Julius Caesar was assassinated, Augustus, Caesar's adopted son, took charge. He did not call himself a dictator or a king. He called himself emperor. He was the first Roman emperor.
Cicero did not care if Rome's leader called himself a dictator, a king, or an emperor. Cicero continued to speak out against the rule of one man and spoke strongly for the virtues of a republic form of government for Rome. Cicero was assassinated because of his speeches against the emperor.