Why did Mark Antony come into conflict with Octavian after Caesar's death?

The conflict between Mark Antony and Octavian emerged from a fundamental struggle for power following the assassination of Julius Caesar. The tension began immediately when Antony, as Caesar’s chief lieutenant, seized his papers and assets, refusing to share funds with Octavian, who had been named Caesar’s adopted son and primary heir.1

While the two men formed the Second Triumvirate to consolidate control, their alliance was marked by deep-seated rivalry. The relationship deteriorated as Octavian systematically undermined Antony’s standing in Rome. Key factors included:21

• Political Rivalry: Octavian engaged in a sophisticated propaganda war, portraying Antony as a man who had abandoned Roman values to become a Hellenistic king under the influence of Cleopatra.23
• Territorial Disputes: Antony’s decision to base himself in the East and his "Donations of Alexandria"—where he distributed Roman territories to Cleopatra and their children—convinced many in Rome that he intended to move the capital to Egypt.24
• Personal Betrayal: Antony’s divorce of Octavian’s sister, Octavia, and Octavian’s public exposure of Antony’s will, which allegedly confirmed his intent to be buried in Egypt, finalized the rupture.34

Ultimately, Octavian’s calculated efforts to position himself as the defender of Roman interests led to the decisive Battle of Actium in 31 BCE.23