Why did Octavian declare war on Cleopatra instead of directly declaring war on Mark Antony?

Octavian declared war on Cleopatra rather than Mark Antony to avoid the appearance of initiating another Roman civil war, which would have been deeply unpopular with the Roman public.12

By framing the conflict as a war against a foreign queen, Octavian successfully shifted the narrative from a personal power struggle between two Roman leaders to a patriotic defense of Rome against an external threat. This strategy was supported by a sophisticated propaganda campaign that depicted Antony as being under the manipulative influence of Cleopatra.12

Octavian utilized several key tactics to justify this distinction:
* Propaganda: He portrayed Antony’s actions—such as the "Donations of Alexandria," where Roman territories were gifted to Cleopatra and her children—as a betrayal of Roman interests in favor of a foreign power.13
* The Will: Octavian seized a document he claimed was Antony’s will, which allegedly stated Antony’s intent to be buried in Alexandria and to transfer Roman lands to Cleopatra’s children.123
* Religious Framing: Octavian contrasted his own devotion to traditional Roman values and the god Apollo with Antony’s association with the foreign deity Dionysus.2

By declaring war on Cleopatra, Octavian forced Antony into the position of fighting against his own country, effectively isolating him from his remaining Roman supporters.12