Over two thousand years ago, a group of aristocrats surrounded Gaius Julius Caesar at a meeting of the Roman Senate and stabbed him to death, having conspired to overthrow a dictator and reestablish a republic. Within a few years of their action, all of the conspirators were dead, and Caesars ruled the world for centuries. Caesar's staying power is visible even today. Among the otherwise-mindless topics "trending" on Twitter today, this morning was filled with trending topics including "Julius Caesar" and the "Ides of March", while a current trending topic is #ReasonsYouGetStabbed. I find this utterly remarkable given that I think you would be hard-pressed to find another person outside of Jesus Christ who has been dead for so long, or for even half as long, and is still so alive in the public imagine. It's a testament to how much the conspiracy of Brutus and Cassius failed in its mission to end Caesar. While there are a multitude of reasons that the Republicans were unable to overcome the Caesarians, these three mistakes from the offset really doomed their dreams:
1. The refusal to include Cicero in the conspiracy was a major mistake. Cicero's gift of oratory surpassed even Caesar's, and he was regarded as one of the most intelligent and patriotic men in Rome--the only other Roman other than Caesar to receive the honorific title Pater Patriae for his defeat of the Catiline Conspiracy. He was the voice of reason. However, Cicero was vain and ambitious, and a wishy-washy flake on top of it. If he were to join the conspiracy, he would want to be in charge of it--and he may have been too queazy to go along with its final mission. In Shakespeare's telling of the tale, Brutus also objects to Cicero's inclusion because he does not want the conspiracy to be led by reason; he wants it to be led by honor. The goodness of the conspiracy's goals should not have to be explained; it should be self-evident. However, by refusing to include Cicero, they lost out on his wise counsel and were also unable to employ him in the ensuing arguments with the Caesarians for the public mind.
2. The failure to kill Mark Antony, Caesar's trusted lieutenant, was a huge oversight. Cassius--and Cicero--said that the man ought to die alongside Caesar, for he was too dangerous to be kept alive. But, the conspirators--again, guided by honor and not reason--did not want to come across as butchers. Brutus would not allow it; if Caesar was dead, they thought that the drunken and vulgar Antony would be unable to do much. They greatly underestimated Antony's power, anger, and ambition, something I am sure that Brutus and Cassius realized as Antony's army wiped their own out.
3. Finally, allowing Antony not only to live but to speak was a huge blunder, and Shakespeare shows that well. There is no historical record of Antony's actual speech, but the effects of it are exactly what Shakespeare described. Antony, speaking at Caesar's funeral with the permission of victorious Brutus, turned the mob against the conspirators and ran them out of the city. He set the public interpretation of the assassination into stone, and his control of the story lasted for centuries. Even in Renaissance Italy, the conspirators were looked upon with hatred--Dante puts Cassius and Brutus on either side of Judas in the mouth of the Beast on the deepest level of Hell. Without Cicero's silver tongue to combat the passionate cries of Antony, who played up the mutual love between Caesar and his people, the conspirators were hopeless and were forced to give up the very thing they sought to keep: Rome.
Of course, there are other factors at play---Cicero's miscalculation of Octavian's skill and ambition, the formation of the Second Triumvirate, the too-far-gone degradation of Roman political society. Nonetheless, these three things doomed the conspiracy from the beginning. However noble their intentions, they failed. They did not murder Antony, and they could not give a proper defense of why they could murder Caesar and not Antony. The result is that two thousand years later, Caesar is still looked at with ambiguous awe while Brutus very much tends to be associated more with betrayal than with patriotism or liberty. High-minded, noble, patriotic Brutus was a good man in an impossible situation, and he could not (or would not) bring himself to do what was practical (and, perhaps, ignoble) in order to defeat Caesar's name, and for that he and his cohorts all met rather unpleasant ends. That's the tragedy of the Ides of March right there.