Gnaeus Domitius Ahenobarbus was a staunch Republican and enemy of Julius Caesar. After Caesar's assassination, he joined the Liberators and was given command of a massive fleet in the Adriatic Sea.
During the Liberators' Civil War, his blockade played a decisive role in cutting off supplies from Italy to the Triumvirate forces in Macedonia, creating the shortages that forced the Battle of Philippi.
After the defeat of Brutus and Cassius, he continued to lead an independent fleet for some time before reconciling with Mark Antony. He initially supported Antony against Octavian but, disillusioned by Cleopatra's influence and suffering from illness, he defected to Octavian shortly before the Battle of Actium. He died of fever soon after, but his defection was a major propaganda blow to Antony.