Marrying your enemy's sister and other Roman political tricks

Roman aristocrats used marriage to turn rivals into allies or remove them as threats.

They did not depend on friendship or persuasion. Instead, they created forced loyalty through blood ties.

In 59 BC, Gaius Julius Caesar arranged the marriage of his daughter Julia to Gnaeus Pompeius Magnus, also known as Pompey the Great.

Pompey had already achieved major military success, and he had begun to drift away from Caesar’s political program.

To secure Pompey’s support, Caesar offered Julia, even though she was still young and Pompey had already become engaged to another woman. 

That marriage briefly kept the First Triumvirate together, a political alliance between Caesar, Pompey, and Marcus Licinius Crassus.

Julia’s death in 54 BC ended the family connection, and within two years, civil war erupted between Caesar and Pompey. 

In 40 BC, Gaius Octavius, known later as Augustus, married his sister Octavia Minor to Marcus Antonius, or Mark Antony.

The purpose was to keep the Second Triumvirate united. Antony had already begun a relationship with Cleopatra VII of Egypt, but Octavian used the marriage to limit his plans and to create a public duty.

When Antony returned to Cleopatra and divorced Octavia, Octavian accused him of disloyalty and used the insult as justification for war.

The fight ended in 31 BC at the Battle of Actium, when Octavian defeated Antony’s forces and claimed power alone in Rome. 

Romans rarely treated marriage as a private affair. It acted as a political weapon.

The women involved received no choice. Their role was to ensure peace, reward allies, or expose betrayal.

They turned family into a tool of statecraft and used marriage to control the Senate as effectively as they controlled armies. 

Daughters were used as negotiating tools in Roman politics as well, as their fathers arranged marriages to influence rivals or reinforce their own power.

The men who controlled political life regarded their daughters’ futures as extensions of their own strategy. 

Lucius Cornelius Sulla, who became the first man to seize supreme power by force, arranged the marriage of his daughter Cornelia to secure an alliance with a reliable supporter.

Julius Caesar also used marriage as a political tool. Before he offered Julia to Pompey, he had considered other marriage options that would benefit his position.

He used her to strengthen a political alliance instead of protecting her future. 

The emperors followed the same pattern. Augustus married his daughter Julia the Elder first to Marcellus, then to Marcus Agrippa, and finally to Tiberius.

Each aimed to strengthen power and remove challenges to his chosen successor.

Julia gave birth to Gaius and Lucius Caesar, the sons of Agrippa, and Augustus promoted them as future emperors.

Their deaths forced him to rely on Tiberius, whom he had little affection for but needed to maintain stability. 

By using daughters to bind powerful men to their families, Roman politicians redefined family life as a means of public control.

Fathers treated their daughters as assets in a system based on loyalty and inheritance to support political aims.

Sadly, marriage did not protect them. It exposed them to the plans and schemes of men who governed the fate of the empire. 

To the suprise of many people today, Roman adoption often involved grown men.

Politicians adopted adults in order to secure heirs, neutralise rivals, or start new dynasties.

In the absence of reliable sons, they chose proven candidates to continue their work. 

The most influential example occurred in 44 BC, when Julius Caesar adopted Octavian in his will.

Although Octavian was only eighteen, and not his biological child, the adoption gave him Caesar’s name, his fortune, and his claim to political leadership.

Octavian used that authority to rally Caesar’s veterans, defeat his rivals, and take control of the Roman state. 

Later, Octavian, as Augustus, adopted Tiberius after the deaths of his earlier heirs.

Tiberius was his stepson and had already proved himself in military service.

Augustus adopted him out of necessity instead of affection becuase he desperately needed to secure the succession to avoid civil unrest. 

The pattern continued in the imperial period. Emperor Nerva adopted Trajan in 97 AD to prevent instability.

Trajan already had a good reputation with the army, and the adoption gave the army a reason to support the new regime.

Trajan later adopted Hadrian, who in turn adopted Antoninus Pius on the condition that he would adopt Marcus Aurelius.

This created a succession of emperors who ruled through merit and consent rather than inheritance alone. 

When relatives became threats, Roman rulers used violence to remove them. One of the most shocking cases involved Nero, the last Julio-Claudian emperor, who ordered the murder of his mother, Agrippina the Younger. 

Agrippina had planned Nero’s rise by marrying Emperor Claudius and persuading him to adopt Nero.

When Claudius died in 54 AD, Nero took the throne at the age of sixteen.

Agrippina expected to dominate him and direct the affairs of state. As Nero matured, he rejected her control because he resented her interference and feared that she might support a rival claimant. 

When his attempts to kill her with poison and a collapsing boat failed, Nero had her stabbed to death in 59 AD.

He accused her of plotting against him, but few believed the charge. The act eliminated the one person who had made his rule possible.

It also removed the last obstacle to his absolute control over the court. 

Other emperors engaged in similar crimes. Caracalla murdered his younger brother Geta during a meeting with their mother present, while Commodus used violence to distance himself from relatives and advisors who tried to manage his unpredictable behaviour.

In each case, personal bloodshed secured political independence.