In 44 BC, the conspiracy to assassinate Julius Caesar is discovered and dealt with and thus never happens. Caesar being and ambitious man, decides to use the conspiracy and the fact that many senators were involved to his advantage. He tells the angry people of Rome that the Senate can no longer be trusted to care for Rome, so he proclaims himself emperor and abolishes the senate.
Julius Caesar would have also been preparing for the big project of his life, one which he never lived to accomplish: the conquest of the Parthian Empire.
In 43 BC, he is ready with a large army and he crosses the Euphrates river. He captures Babylon with ease. He marches towards the Tigris river and on the banks of that river he battles a large Parthian army. He is victorious. He marches to Ctesphon the Parthian capital (Built on the banks of the Tigris rver) and finds it empty and razed. Caesar finds out that the Parthian king has moved his court and Ctesphon's inhabitants to Susa and has greatly fortified his new capital. Julius Caesar realizes that his supply line is starting to thin. So he returns to stay at Babylon, until the following year.
In 42 BC, Julius Caesar finds a large Parthian army including Arab mercenaries and Indian war elephants waiting for him at the other side of the Tigris river. It was a battle called the Battle of Gophrys for it was fought near a small hamlet west of the river called Gophrys. During the battle, Marc Anthony saved Caesar's life. In the end, Caesar won, but it was a Pyrhhic victory because Caesar lost most of his men. A week later, the king of Parthia sent an emissary to Caesar asking to parlay. Caesar agreed, and the two leaders met in the ruins of Ctesphon. There they agreed to allow the Roman Empire to keep the land west of the Tigris and bother Parthia no more. They also agreed that the Parthian king would give one ton of spices and half a ton of silver to Rome.
Julius Caesar returned to Babylon with his remaining men and there he feasted. He called the new territory the province of Mesopotamia. He then gave the provinces of Syria and Mesopotamia to Marc Anthony. He then returned to Rome.
In Rome, Cleopatra (who was living with Caesar in Rome) demanded that he (Julius Caesar) name her son Caesarion as his heir instead of Octavian. Julius Caesar refused. So in the summer of 42 BC, Cleopatra sailed back to Alexandria. That same year, she went to see Marc Antony at Babylon. There she seduced him and convinced him to join her in a revolt against Caesar and make himself emperor.
In 41 BC, Cleopatra briefly returned to Rome. There she feigned apology to Caesar for the way she acted. But in reality she poisoned his wine. Each day a small pinch until a month later he was dead.
Unfortunately, Cleopatra had not calculated what would happen next. Octavian took the throne and promised to avenge Caesar. Cleopatra fled Rome with haste.
Finally in 40 BC, they were ready. In that year, Marc Antony declared to the legions in the East that he was the Caesar's true heir and Cleopatra his consort. They fully supported him. Antony spent the rest of the year winning support from the Hellenic kingdoms in Asia Minor, from King Herod of Judea and King Aretas of Nabatea. Antony even enlisted the support of the Parthians.
In 39 BC, with an army of 450,000 men, he marched on Greece. At Byzantion , Antony was ambushed by Octavian's army and navy. It was a total slaughter, with Antony losing half his army. Octavian landed more troops at Ephesus and Smyrna. This encouraged the Hellenic kings of Asia Minor to switch allegiances to Octavian. Antony retreated to Antioch in Syria.
In 38 BC, riots tore apart Babylon. Even Antony's soldiers took part. It was primarily because Antony had shown himself an atrocious general and now he had aligned himself with the hated Parthians. Meanwhile, Octavian marched towards Antioch. Judea and Nabatea also switched allegiances and joined Octavian. In Babylon, Heliodorus of Athens, who Antony had left in charge of the province of Mesopotamia in his absence wrote a long letter to Octavian making excuses and stating that he too would promptly switch sides. So fearing for his life, Antony boarded a ship by night and sailed to Alexandria to be with Cleopatra.
When Octavian arrived at Antioch, they opened the gates to him. When he found that Marc Antony was not there, he was livid.
Ironically, the only ally Antony and Cleopatra had left was the Parthians. Using their allegiance to Antony as a pretext, they crossed the Tigris river with a massive army and marched into Babylon. They executed the rioters and had Heliodorus of Athens drowned in the Euphrates river. At this point, King Herod of Judea and King Aretas of Nabatea declared that they were neutral.
In 37 BC, Octavian was forced to turn east to deal with the Parthians. At night he crossed the Euphrates with his army and surprised the Parthians at Babylon. He besieged the city and captured it. During the battle to take the city, King Arsaces XXII of Parthia was slain. This threw the Parthians into disarray. Babylon and all land west of the Tigris was retaken by Octavian. King Arsaces XXIII signed a treaty with Octavian.
In 36 BC, Ocavian went through Jerusalem on his way to Egypt. In desperation, Cleopatra sent a lot of gold and gems along with a letter to King Herod telling him he could keep the gold and gems if he murdered Octavian while he was a guest in Herod's house. Herod promptly showed the letter to Octavian who promised to give Herod the double the gold and gems offered in return for his loyalty.
Octavian continued through Judea on his way to Egypt. Antony and Cleopatra threw together a last second army to meet Octavian's army at Pelusium. Octavian won and during the battle Antony was killed.
Cleopatra had 2 years worth of provisions in Alexandria and so she shut herself in the city and waited. Octavian besieged the city for two years. Then the food ran out.
In 34 BC, the people of Alexandria had enough. They attacked the royal palace and seized Cleopatra. Then they opened the gates of the city to Octavian and brought Cleopatra to him. Octavian accused her of starting this whole war and then in front of the shocked crowd he beheaded her and proclaimed himself emperor of Rome and pharaoh of Egypt.
In 33 BC, Octavian returned to Rome in triumph where he took the name Augustus and began his rule.
In 29 BC, a riot took place in Rome with much looting and social unrest. The riot had been started by ex-senator Cicero. It was demanding the reinstatement of the Senate. Augustus (Octavian) realized it would be political suicide to refuse. So he acquiesced their demands. Cleverly, he left the Senate with an advisory role leaving him with all the real power.
In 21 BC, The Roman governor of Mesopotamia was murdered. This left the province in disarray. Desiring revenge for the death of his brother, King Arsaces XXIII of Parthia invaded Mesopotamia and took Babylon. Then from there he crossed the Euphrates and went into Syria. Antioch surrendered without a fight. A second army came from Parthia led by Arsaces's cousin Oronius. This entire time, Augustus was in Gaul putting down a revolt. Oronius advanced on Judea and took Jerusalem. He held King Herod captive in Jerusalem while he was there.
King Attalus of Galatia realized he was in Arsaces's path came up with a plan. In December of 21 BC, he wrote a long letter to Arsaces flattering the king of Parthia and inviting the king and his nobles to his palace for a new years eve feast. He requested however, that Arsaces leave his army behind because "The military presence might scare his people". Amazingly enough Arsaces agreed and showed up. It was an extremely extravagant party and Attalus spared no expense.
Finally, in the first hour of the morning (January 1st 20 BC) when King Arsaces and his nobles were so drunk they could hardly stand. Attalus gave an order, his guards came in and slaughtered the king of Parthia and all his nobles. While the servants cleaned up the mess, Attalus forged a letter in Arsaces's name saying that he was staying with Attalus for a time. As a result, The Parthian army remained camped on the border of Galatia doing nothing the entire time. In the absence of their king they lapsed into laziness and carelessness. On the night of January 12th, Attalus and his much smaller army ambushed the drunken Parthians and butchered them and seized their spoil.
In Jerusalem, Oronius heard all the things that Attalus had done and so he got up and with his entire army left Judea and went to Babylon. Augustus finally came with his army, landed at Alexandria and came into Judea and Palestine sweeping all the remaining pockets of Parthian troops. Augustus attempted to cross the Euphrates with his men but this time he lost to the Parthians.
In 19 BC, Oronius who had confirmed himself as king of Parthia signed a peace treaty with Augustus.