After years of loyal cooperation with Octavian, Antony started to act independently, eventually arousing his rival's suspicion that he was vying to become sole master of Rome. When he left Octavia Minor and moved to Alexandria to become Cleopatra's official partner, many Roman politicians suspected that he was trying to become the unchecked ruler of Egypt and other eastern kingdoms while still maintaining his command over the many Roman legions in the East. As a personal challenge to Octavian's prestige, Antony tried to get Caesarion accepted as a true heir of Caesar, even though the legacy did not mention him. Antony and Cleopatra formally elevated Caesarion, then 13, to power in 34 BC, giving him the title "King of the Kings" (Donations of Alexandria). Such an entitlement was seen as a threat to Roman republican traditions. It was widely believed that Antony had once offered Caesarion a diadem. Thereafter, Octavian started a propaganda war, denouncing Antony as an enemy of Rome and asserting that he intended to establish a monarchy over the Roman Empire on Caesarion's behalf, circumventing the Roman Senate. It was also said that Antony intended to move the imperial capital to Alexandria.