According to legend, a soothsayer had warned Caesar to "beware of Ides Of March". Under the Roman calendar, the Ides marked as middle of the month, the date he was brutally murdered. The story of the soothsayer was probably a later invention, but the conspirators certainly commemorated the Ides of March as the day they killed Julius Caesar.
The assassination of Julius Caesar was the result of a conspiracy by many Roman senators. It was led by Gaius Cassius Longinus and Marcus Junius Brutus.