The Crime of Killing Marcus Agrippa Postumus
Marcus Agrippa Postumus was the actual grandson of Augustus. Born in 12 BC after his father, Marcus Vipsanius Agrippa, had already died, he received the name Postumus for that reason. Augustus later adopted him, making the young man both biological grandson and legal son. Ancient writers painted him in dark colours—brutish, fierce, uncultivated—yet recorded no clear crime that justified his fate. He was simply inconvenient.
In AD 6 Augustus banished him, first to Surrentum and then under permanent military guard to the island of Planasia. Shortly after Augustus died on 19 August AD 14, Postumus was killed by his own guards. Tacitus called it the first crime of the new principate. It would not be the last under Tiberius. The question remains: why? One persistent suggestion is that the killing satisfied Livia, who wanted her son Tiberius on the throne without a blood rival who still carried the direct descent of Augustus. By then the succession had already been settled in Tiberius’s favour, yet Postumus’s continued existence was treated as a residual threat that needed removing.
Not every potential rival was disposed of so cleanly. Caligula and Nero—direct descendants of Mark Antony through his daughters with Octavia—were shepherded toward the throne. Antony himself had taken his own life in 30 BC after Actium, an act that may have been intended, among other things, to shield what remained of his family from further official vengeance. His bloodline, however, survived and eventually wore the purple. Nero reached the throne with the energetic help of his mother, Agrippina the Younger, only to have her killed later. Caligula, by contrast, is said to have tried to protect his own mother, Agrippina the Elder, though ultimately in vain.
Maternal ambition in dynastic politics is an old and recurring pattern. The historical record offers many clear examples of mothers who worked, sometimes ruthlessly, to place or keep a son in power:
- Margaret Beaufort, mother of Henry VII of England, spent decades advancing her son’s distant Lancastrian claim during the Wars of the Roses. She forged alliances, raised support and money for his invasion, and helped secure the victory at Bosworth in 1485 that founded the Tudor dynasty.
- Agrippina the Younger, great-granddaughter of Augustus, married her uncle Claudius, secured the adoption of her son Nero over Claudius’s biological son Britannicus, and is accused by ancient sources of poisoning Claudius so that Nero could succeed. She dominated the early years of his reign before their relationship collapsed and he ordered her death.
- Olympias, mother of Alexander the Great, vigorously promoted her son’s position as heir to Philip II. After Philip’s assassination she moved quickly to eliminate rivals and continued to intervene forcefully on behalf of Alexander’s line after his death.
- Bathsheba, in the biblical account of 1 Kings 1–2, intervened with the aging David when Adonijah moved to claim the throne. Working with the prophet Nathan, she reminded the king of a promised succession for Solomon and secured his anointing.
- Catherine de’ Medici, after the death of Henry II, became the dominant political force during the reigns of her three successive sons amid the French Wars of Religion, serving as regent and using every available instrument to keep the Valois dynasty on the throne.
- Empress Matilda, daughter and designated heir of Henry I, fought the long civil war known as the Anarchy. Though she never fully secured the crown for herself, her persistence forced recognition of her son Henry as Stephen’s heir; he succeeded as Henry II and founded the Angevin Empire.
Other notable cases include Galla Placidia as active regent for Valentinian III; Julia Soaemias (with her mother Julia Maesa) engineering the rise of Elagabalus; Yolande of Aragon protecting and advancing the claims of the future Charles VII during the Hundred Years’ War; and Töregene Khatun manoeuvring as regent to secure the election of her son Güyük as Great Khan of the Mongol Empire.
These women operated in very different cultures and centuries, yet the pattern is consistent: kinship, regency rights, claims of legitimacy, strategic alliances, and, when necessary, the removal of rivals. Primary sources are frequently hostile or propagandistic toward ambitious royal women, so modern readers must treat them critically. Still, the political agency these mothers exercised is unmistakable.
The killing of Agrippa Postumus sits at one end of this spectrum—the quiet elimination of a inconvenient blood heir so that another mother’s son could rule without challenge. At the other end stand the mothers who actively engineered their sons’ rise, sometimes only to be destroyed by the very power they had created. Dynastic politics has never been a gentle business, and maternal ambition has often been one of its sharpest instruments.



