Very few Roman emperors died natural deaths. Most were assassinated, some died in battle and one was even struck by lightning. Some emperors sensed the danger and got out of Rome altogether. But only one laid down his power and retired. Diocletian, who ruled for 20 years in the late third and early fourth centuries CE, went back to his home town to grow cabbages.A dangerous jobIn a highly militaristic and competitive society, it is perhaps no surprise Rome’s rulers sometimes met violent ends. Eccentricity, military failures and economic problems saw their allies abandon them.Caligula (37–41 CE), Domitian (81–96 CE) and Caracalla (who was sole emperor from 211–217 CE) were killed in conspiracies hatched by their bodyguards. Severus Alexander (222–235 CE) and Gallienus (253–268 CE) were killed by senior military officers. Some emperors met untimely ends at the hands of foreign enemies. Gordian III (238–244 CE) died in battle against the Persians. Decius (249–251 CE) and Valens (364–378 CE) died fighting the Goths (a Germanic people that conducted frequent raids on Roman territories).Some unusual examples include Carus (282–283 CE) who was reportedly struck by lightning, Claudius II (268–270 CE) who died of plague, and Nero (54–68 CE) who took his own life.The emperor Tiberius (14–37 CE) decided to quit Rome in 26 CE because he feared assassination. He ruled the empire from the island of Capri near Naples until his death 11 years later. The remains of Villa Jovis, where he lived, can still be seen.Some emperors died in office of age-related illnesses, including Constantine in 337 CE and Marcus Aurelius in 180 CE. Both were around 60, which might not seem so old today but it was an advanced age in antiquity.So when Diocletian declared he would abdicate and retire in May 305 CE, it was a highly unusual development. Rise of the tetrarchyDiocletian hailed from the province of Dalmatia in modern Croatia. He came from a humble background and rose through the ranks of the Roman army. A number of third-century emperors came from similar backgrounds. The many crises Rome faced during this period saw seasoned military men become emperor. Diocletian held a range of senior military positions before becoming emperor in November 284 CE. He commanded the army in the important border province of Moesia (modern Serbia and Bulgaria). He was commander of the short-reigning emperor Numerian’s bodyguard when the latter was killed; Diocletian became emperor in his place soon after.Diocletian is traditionally seen as a reformer, making significant administrative, economic and military changes. These reforms tried to address the many problems emperors of the third century faced before him.As emperor, Diocletian introduced a system known as the tetrarchy, which divided the rule of the empire between four emperors. Two were senior (Augusti) and two were junior (Caesars). This limited the possibility of internal revolts and made fighting foreign enemies easier. Scholars now think Diocletian wasn’t quite so innovative; he may have drawn more on reforms developed by his predecessors than was previously thought. But he had clearly been busy over the 20 years he was in power. So, in 305 CE he decided, at around age 60, to hand in his notice and retire.Illness – or divine retribution?As with most ancient stories, it probably wasn’t as simple as that. You can still visit Diocletian’s palace in Split, Croatia, today. Zhivko Dimitrov/Unsplash The ideology of the tetrarchy was also about renewal. The other senior Augustus, Maximian, abdicated at the same time as Diocletian. The two junior rulers, Galerius and Constantius I, became the senior rulers and two new junior rulers were recruited. This became known as the Second Tetrarchy. Diocletian had also suffered a prolonged illness before his abdication. He had taken ill early in 304 CE and wasn’t seen in public for months. As one of the emperors responsible for horrific persecution of the Christians in 303–4 CE, this was seen by some as divine retribution.Diocletian retired to an impressive palace at Spalatum (modern-day Split in Croatia) near his home town of Salona in Dalmatia. Its extensive remains can still be visited today. It was here that he famously grew cabbages.Choosing cabbages over chaosA later historical account claimed Diocletian was asked to come out of retirement to deal with a political stalemate. The second tetrarchy had quickly descended into chaos. But Diocletian wanted nothing of it, reportedly replying:If you could see at Salona the cabbages raised by our hands, you surely would never judge that a temptation.Diocletian had grown to love the quiet life after years of reforms and the ever-present possibility of assassination. Retiring to grow cabbages was far more appealing.And cabbages were seen as a miracle food in ancient Rome. Their health benefits were known to many, and ancient recipes using them are still available today.Diocletian was unique in Roman imperial history for choosing retirement. He would die in 313 CE approaching the age of 70, his last years ones of contentment. Knowing when time is up remains a key challenge for leaders to this day. For many, the trappings of power remain too tempting compared with life’s simple joys.Peter Edwell receives funding from the Australian Research Council.