The Great Roman Civil War (49–45 BCE), also known as Caesar's Civil War, one of the last politico-military conflicts in the Roman Republic before the establishment of the Roman Empire, begins as a series of political and military confrontations between Julius Caesar, his political supporters (broadly known as Populares), and his legions, against the Optimates (or Boni), the politically conservative and socially traditionalist faction of the Roman Senate, who are supported by Pompey and his legions.

Caesar is appointed dictator in Rome, with Mark Antony as his Master of the Horse; Caesar presides over his own election to a second consulate (with Publius Servilius Vatia as his colleague), then, after eleven days, resigns this dictatorate.

He pursues Pompey to Alexandria, where Pompey is murdered by a former Roman officer serving in the court of King Ptolemy XIII.

Caesar then becomes involved with the Alexandrine civil war between Ptolemy and his sister, wife, and co-regent queen, the Pharaoh Cleopatra VII.

Caesar sides with Cleopatra, perhaps as a result of Ptolemy's role in Pompey's murder; he is reported to have wept at the sight of Pompey's head, which is offered to him by Ptolemy's chamberlain Pothinus as a gift.

In any event, Caesar withstands the Siege of Alexandria, later defeating the Ptolemaic forces in 47 BCE in the Battle of the Nile and installing Cleopatra as ruler.

Caesar and Cleopatra never marry, as Roman Law only recognizes marriages between two Roman citizens, but he continues his relationship with Cleopatra throughout his last marriage, which lasts fourteen years—in Roman eyes, this does not constitute adultery—and may have fathered a son called Caesarion.

Cleopatra visits Rome on more than one occasion, residing in Caesar's villa just outside Rome across the Tiber.

Caesar had again been appointed Dictator late in 48 BCE, with a term of one year.

After spending the first months of 47 BCE in Egypt, Caesar crosses to Asia, where he annihilates King Pharnaces II of Pontus in the Battle of Zela; his victory is so swift and complete that he mocks Pompey's previous victories over such poor enemies.

He thence proceeds to Africa to deal with the remnants of Pompey's senatorial supporters.

He quickly gains a significant victory at Thapsus in 46 BCE over the forces of Metellus Scipio (who dies in the battle) and Cato the Younger (who commits suicide).

After this victory, Caesar is appointed Dictator for ten years.

Mediterranean Southwest Europe (57–46 BCE): Caesar's Civil War and the Collapse of the Republic

The era 57–46 BCE marks one of the most critical periods in the history of the Roman Republic, dominated by the turmoil and transformation brought about by Caesar's Civil War. This conflict, fundamentally political and military, pits Julius Caesar and his supporters—the Populares—against the conservative faction of the Senate—the Optimates—led militarily by Pompey the Great.

Outbreak of Civil War and Caesar’s Dictatorship

The conflict erupts in 49 BCE, after prolonged political tensions between Caesar and the Senate culminate in Caesar’s dramatic crossing of the Rubicon River, symbolically declaring war against Rome itself. Pompey and most senators flee Rome, regrouping in Greece and other parts of the Republic.

In Rome, Caesar rapidly consolidates power, assuming the role of dictator and appointing Mark Antony as his Master of the Horse. After presiding briefly over his election to a second consulate alongside Publius Servilius Vatia, Caesar resigns the dictatorship after eleven days, though retaining supreme authority through military dominance.

Pompey's Defeat and Death in Egypt

Caesar pursues Pompey to Egypt, arriving in Alexandria shortly after Pompey’s assassination at the hands of the court of Ptolemy XIII. Caesar aligns himself with Cleopatra VII, Ptolemy’s sister and rival, becoming embroiled in the Alexandrine civil war. After surviving a challenging siege, Caesar decisively defeats Ptolemy’s forces at the Battle of the Nile in 47 BCE, establishing Cleopatra firmly as ruler of Egypt.

Despite never marrying due to Roman legal constraints—Roman law only recognizes marriages between Roman citizens—Caesar maintains a significant relationship with Cleopatra, who later visits Rome, residing in Caesar’s villa across the Tiber. Caesar and Cleopatra’s union is historically notable, and Caesar is believed to have fathered a son, Caesarion, with her.

Caesar’s Campaigns and Dictatorship

Caesar’s authority continues to solidify. After his victory in Egypt, he swiftly moves to Asia Minor, defeating King Pharnaces II of Pontus at the Battle of Zela with remarkable speed, famously summarized by his phrase, "Veni, vidi, vici" ("I came, I saw, I conquered").

Returning westward, Caesar decisively confronts and defeats the last remnants of Pompey’s senatorial allies at the Battle of Thapsus in Africa in 46 BCE, where key opponents such as Metellus Scipio and Cato the Younger perish—Scipio in battle and Cato by suicide.

Following Thapsus, Caesar is appointed dictator for ten years, securing unprecedented control over the Roman Republic, effectively signaling the Republic's transition into a period of singular authority.

Expansion and Colonization

Meanwhile, Roman colonization efforts continue. Como, situated in the Lombardy region of northern Italy near Lake Como and historically inhabited by the Celtic Orobii tribe, becomes a Roman colony during this period, indicative of Rome’s continuing expansion and consolidation of its northern territories.

Legacy of the Era

The period 57–46 BCE profoundly reshapes the Roman Republic. Caesar’s victories not only eradicate the immediate political and military opposition but also lay the foundation for a fundamental transformation of Roman governance. Caesar’s ascendance and extended dictatorship directly precipitate the demise of the Republic, paving the way for imperial rule and permanently altering Rome’s historical trajectory.

Mediterranean Southwest Europe (57–46 BCE): Caesar's Civil War and the Collapse of the Republic

The era 57–46 BCE marks one of the most critical periods in the history of the Roman Republic, dominated by the turmoil and transformation brought about by Caesar's Civil War. This conflict, fundamentally political and military, pits Julius Caesar and his supporters—the Populares—against the conservative faction of the Senate—the Optimates—led militarily by Pompey the Great.

Outbreak of Civil War and Caesar’s Dictatorship

The conflict erupts in 49 BCE, after prolonged political tensions between Caesar and the Senate culminate in Caesar’s dramatic crossing of the Rubicon River, symbolically declaring war against Rome itself. Pompey and most senators flee Rome, regrouping in Greece and other parts of the Republic.

In Rome, Caesar rapidly consolidates power, assuming the role of dictator and appointing Mark Antony as his Master of the Horse. After presiding briefly over his election to a second consulate alongside Publius Servilius Vatia, Caesar resigns the dictatorship after eleven days, though retaining supreme authority through military dominance.

Pompey's Defeat and Death in Egypt

Caesar pursues Pompey to Egypt, arriving in Alexandria shortly after Pompey’s assassination at the hands of the court of Ptolemy XIII. Caesar aligns himself with Cleopatra VII, Ptolemy’s sister and rival, becoming embroiled in the Alexandrine civil war. After surviving a challenging siege, Caesar decisively defeats Ptolemy’s forces at the Battle of the Nile in 47 BCE, establishing Cleopatra firmly as ruler of Egypt.

Despite never marrying due to Roman legal constraints—Roman law only recognizes marriages between Roman citizens—Caesar maintains a significant relationship with Cleopatra, who later visits Rome, residing in Caesar’s villa across the Tiber. Caesar and Cleopatra’s union is historically notable, and Caesar is believed to have fathered a son, Caesarion, with her.

Caesar’s Campaigns and Dictatorship

Caesar’s authority continues to solidify. After his victory in Egypt, he swiftly moves to Asia Minor, defeating King Pharnaces II of Pontus at the Battle of Zela with remarkable speed, famously summarized by his phrase, "Veni, vidi, vici" ("I came, I saw, I conquered").

Returning westward, Caesar decisively confronts and defeats the last remnants of Pompey’s senatorial allies at the Battle of Thapsus in Africa in 46 BCE, where key opponents such as Metellus Scipio and Cato the Younger perish—Scipio in battle and Cato by suicide.

Following Thapsus, Caesar is appointed dictator for ten years, securing unprecedented control over the Roman Republic, effectively signaling the Republic's transition into a period of singular authority.

Expansion and Colonization

Meanwhile, Roman colonization efforts continue. Como, situated in the Lombardy region of northern Italy near Lake Como and historically inhabited by the Celtic Orobii tribe, becomes a Roman colony during this period, indicative of Rome’s continuing expansion and consolidation of its northern territories.

Legacy of the Era

The period 57–46 BCE profoundly reshapes the Roman Republic. Caesar’s victories not only eradicate the immediate political and military opposition but also lay the foundation for a fundamental transformation of Roman governance. Caesar’s ascendance and extended dictatorship directly precipitate the demise of the Republic, paving the way for imperial rule and permanently altering Rome’s historical trajectory.

Caesar follows his Optimate opponents to Africa after his rapid pacification of the Eastern provinces, and a short visit to Rome, landing in Hadrumetum (modern Sousse, Tunisia) on December 28, 47 BCE.

The Optimates gather their forces to oppose Caesar with astonishing speed.

Their army includes forty thousand men (about ten legions), a powerful cavalry force led by Caesar's former right hand man, the talented Titus Labienus, forces of allied local kings and sixty war elephants.

The two armies engage in small skirmishes to gauge the strength of the opposing force, during which two legions switch to Caesar's side.

Meanwhile, Caesar expects reinforcements from Sicily.

Thapsus, originally founded by Phoenicians near a salt lake on a point of land eighty stadia (14.8 km) from the island of Lampedusa, serves as a marketplace on the coast of the province Byzacena in Africa Propria.

In the beginning of February, Caesar arrives in Thapsus and besieges the city, blocking the southern entrance with three lines of fortifications.

The Optimates, led by Metellus Scipio, cannot risk the loss of this position and are forced to accept battle.

Caesar's archers attacks the elephants, causing them to panic and trample their own men.

The elephants on the left flank charge against Caesar's center, where Legio V Alaudae is placed.

This legion sustains the charge with such bravery that afterwards they will wear an elephant as a symbol.

After the loss of the elephants, Metellus Scipio starts to lose ground.

Caesar's cavalry outmaneuvers its enemy, destroys the fortified camp, and forces its enemy into retreat.

King Juba's allied troops abandon the site and the battle is decided.

Roughly ten thousand enemy soldiers want to surrender to Caesar, but are instead slaughtered by his army.

This action is unusual for Caesar, who is known as a merciful victor.

Some sources contend Caesar had an epileptic seizure during the battle and was not fully conscious for its aftermath.

Scipio himself escapes, only to commit suicide months later in a naval battle near Hippo.

Following the battle, Caesar renews the siege of Thapsus, which eventually falls.

Caesar exacts a payment of fifty thousand sesterces from the vanquished.

Their defeat marks the end of opposition to Caesar in Africa.

Thapsus now becomes a Roman colony.

Caesar proceeds to Utica, where Cato the Younger is garrisoned.

On the news of the defeat of his allies, Cato commits suicide.

Caesar is upset by this and is reported by Plutarch to have said: Cato, I must grudge you your death, as you grudged me the honor of saving your life.

The battle precedes peace in Africa—Caesar pulls out and returns to Rome on July 25 of the same year.

Opposition, however, will rise again.

Titus Labienus, the Pompeian brothers and others have managed to escape to the Hispania provinces.

The civil war is not finished, and the Battle of Munda will soon follow.

King Juba, who had been a supporter of Pompey the Great against Julius Caesar, has attempted to establish a strong, independent Numidian state.

After Caesar defeats Juba in 46, he forms a new province, Africa Nova, from Numidian territory.

Sallust, who has found refuge in Caesar's army, has participated in Caesar's African campaign and becomes governor of Numidia, which becomes briefly the province of Africa Nova until Augustus restores Juba II (son of Juba I) after the Battle of Actium.