Final answer:
Antony and Octavius, as well as Brutus and Cassius, played crucial roles in ancient Roman history. Antony and Octavius were key in the transition from the Republic to the Empire, while Brutus and Cassius were notable for assassinating Caesar, leading to significant political upheaval.
Step-by-step explanation:
When assessing who played a significant role in ancient Roman history, both Antony and Octavius as well as Brutus and Cassius were pivotal figures. After Julius Caesar's assassination, Mark Antony aligned with Octavian (Caesar's adopted son and heir) and Lepidus to form the Second Triumvirate. This power trio defeated the forces of Brutus and Cassius, effectively ending the reprisal for Caesar's murder. Antony and Octavius's initial alliance, their subsequent rivalry, and Octavian's eventual victory over Antony marked the transition from the Roman Republic to the Roman Empire, with Octavian becoming the first Roman Emperor, Augustus.
The First Triumvirate, which was a different political alliance, consisted of Julius Caesar, Pompey, and Crassus. While this group was instrumental during an earlier time, the actions of the Second Triumvirate were more directly related to the pivotal transformation of Roman political structure and the establishment of imperial rule.