60 BC: First Triumvirate formed between Caesar, Crassius, and Pompey. Caesar is made proconsul of Gaul, Cisalpine Gaul, and Illyricum, commanding four legions. Pompey is made proconsul of Hispania, and Crassius proconsul of Syria.
53 BC: Crassius is killed fighting in Parthia ending the First Triumvirate. Pompey governs Hispania from Rome while Caesar fights in Gaul.
52 BC: Caesar commands ten legions and defeats Vercingetorix at Alesia, ending the Gallic Wars. Cato, Pompey, and Scipio lead a Senate faction opposed to Caesar's "populist policies". The Senate demands Caesar disband and return to Rome to answer charges of "war crimes". Caesar refuses to disband arguing he is proconsul of Gaul until 49BC.
50 BC: Caesar now has nine veteran legions, 3000 cavalry, and a 900 man bodyguard. Pompey has seven legions in Hispania, two in Italia, and two in Syria and Africa. Pompey has naval superiority. Senate declares Caesar an enemy of the state.
49 BC: Caesar crosses Rubicon with XIII Legion in January. Pompey retreats from Rome to Brundisium. Caesar besieges Brundisium, but Pompey escapes by ship to Greece. Caesar now marches to Spain, where he forces five Pompey Legions to surrender at Llerda.
48 BC: Caesar and Antonius assemble five legions at Brundisium and ship them to Greece. The Battle of Dyrrachium is fought in July, ending with a Pompey victory. Caesar retreats but then wins a decisive victory at Pharsalus in Thessaly. Pompey flees to Egypt where he is assassinated by command of Ptolemy XIII. Caesar now becomes involved in a civil war between Ptolemy XIII and his sister Cleopatra VII. Caesar supports Cleopatra and defeats Ptolemy XIII who drowns in the Nile.
47 BC: Caesar attacks into Syria and Pontus, defeating Pharnaces II, a petty king who took advantage of the Roman Civil War to expand his power. Pharnaces is crushed at Battle of Zela, said to be the origin of the famous phrase "Veni, Vidi, Vici" (I came, I saw, I conquered).
46 BC: Battle of Thapsus. Caesar invades Africa with 10 legions and defeats Scipio's 14 legions. Scipio & Cato take their own lives. Pompey's son, Sextus Pompey, escapes to Hispania to continue the war.
45 BC: Battle of Munda. Caesar invades Hispania by sea with 8 legions. He defeats Sextus (13 legions) who is killed, ending the war.
44 BC: On the Ides of March, Caesar is assassinated in a conspiracy arranged by Brutus and Cassius. The assassins flee Rome; Antonius and Octavian assume command.
42 BC: Battle of Phillipi. Octavian and Antonius defeat Brutus and Cassius, who both commit suicide. Eleven years later, the two victors fight for supremacy, a struggle that Octavian wins at Actium to become Augustus, the first Emperor of Imperial Rome.