Marcus Antonius (January 14, 83 BC – August 1, 30 BC), commonly known in English as Mark Antony, was a Roman politician and general who played a critical role in the transformation of the Roman Republic from an oligarchy into the autocratic Roman Empire. Antony was an important supporter of and military commander for Julius Caesar during his conquest of Gaul and subsequent civil war. Caesar appointed Antony the administrator of Italy while he eliminated his political opponents in Greece, North Africa, and Spain. After Caesar 's assassination in 44 BC, Antony joined forces with Marcus Lepidus, one of Caesar 's generals, and Caesar 's adoptive son Octavian in a three-man dictatorship known as the Second Triumvirate. The Triumvirate defeated Caesar 's murderers, the Liberatores, at the Battle of Philippi in 42 BC and divided government of the Republic between themselves. Antony was assigned Rome 's eastern provinces, including Rome 's client kingdom of Ptolemaic Egypt ruled by Queen Cleopatra, and command of Rome 's war against Parthia. Relations within the Triumvirate were strained as the various members sought greater political power. Civil war between Antony and Octavian was averted in 40 BC when Antony married Octavian 's sister Octavia Minor. Despite his marriage, Antony continued his love affair with Cleopatra, further straining political ties to Rome. With Lepidus expelled in 36 BC, the Triumvirate finally broke up in 33 BC as disagreements between Octavian and Antony erupted into civil war in 31 BC. The Roman Senate, at Octavian 's direction, declared war on Cleopatra and proclaimed Antony a traitor. Antony was defeated by Octavian at the naval Battle of Actium the same year. Defeated, Antony fled with Cleopatra back to Egypt where he committed suicide. With Antony dead, Octavian was left as the undisputed master of the Roman world. Octavian would assume the title Augustus and would reign as the first Roman Emperor.