Caligula (12 to 41 CE) was the third Roman emperor, who reigned from 37 to 41 CE. A member of the Julio-Claudian Dynasty, he came to power after the death of his great-uncle Tiberius. The ancient sources claim that he was initially a popular ruler, but, after only a few months, he gave in to his sadistic, depraved, and paranoid impulses and began ruling through terror. He was assassinated on 24 January 41 CE by disaffected members of the Praetorian Guard.

The boy who would become Caligula was born Gaius Julius Caesar Germanicus on 31 August 12 CE in Antium. He was the third surviving child of the popular Roman general Germanicus, who, as the nephew and adopted son of Emperor Tiberius, was heir apparent to the Roman Empire. His mother, Agrippina the Elder, was no less distinguished, being the favorite granddaughter of Augustus, the first Roman emperor (or princeps). A handsome and dashing pair, Germanicus and Agrippina were the golden couple of the Roman world, and their children were equally adored. When Germanicus took command of the legions of the Rhine frontier, he brought 2-year-old Gaius along. There, toddling about camp in a miniature army uniform, Gaius won the hearts of his father's soldiers who endearingly nicknamed him 'little military boots', or 'Caligula'.

But the popularity of Germanicus and his family would prove to be their downfall. In October 19 CE, Germanicus fell sick and died while on a diplomatic tour of the eastern provinces. Rumors quickly spread that he had been poisoned, and indeed, Agrippina suspected the complicity of Emperor Tiberius himself. It was no secret that the paranoid old emperor was jealous of his heroic, youthful heir, leading Agrippina to believe that he had quietly ordered her husband's assassination. This unspoken accusation caused a rift between Agrippina and Tiberius that climaxed in 29 CE, when Tiberius exiled her to the island of Pandateria. There, she suffered horribly; according to the historian Suetonius, she was beaten so badly that she lost an eye. She never returned from exile but died of starvation in 33 CE.

Barely into his 20s when his mother died, Caligula understood his proximity to the throne was threatening to the emperor. His two older brothers, Nero and Drusus, had already aroused Tiberius's suspicions and had paid the price – having been declared enemies of the state in 30 CE, they were sent into exile, where they both died after only a few years. Around the same time, Caligula was summoned to the island of Capri, where the reclusive Tiberius held court away from the prying eyes of Rome. It was painfully obvious that the emperor had brought him there not to act as his guardian, but to keep a close eye on his activities. Essentially a hostage, Caligula knew that one misstep, even a disagreeable facial expression, could earn him the same fate as his mother and brothers. As such, he made sure not to show any signs of anger or grief. Suetonius writes that "he behaved as though nothing had happened to his family and that their ruin had quite slipped his mind" (Suet., Life of Gaius, 10).

This devil-may-care attitude helped keep him alive. So, too, did his friendship with the prefect of the Praetorian Guard, Naevius Sutorius Macro. Sensing that an early friendship with the young prince might pave his own way to power, Macro supported Caligula and went to great lengths to convince Tiberius that he was obedient and loyal. Eventually, the emperor lowered his guard enough to arrange a marriage between Caligula and Junia Claudilla, the daughter of the influential senator Marcus Junius Silanus. But still, Tiberius refused to trust Caligula completely and kept him on Capri for seven years. It was during this time, Suetonius claims, that Caligula first showed signs of the "cruelty and deviant appetites" for which he would become infamous:

He took a keen delight in watching the agonies and torments of those condemned to torture, spent his nights disguised in a wig and the robe of a respectable matron, visiting cheap bars and sleeping with other men's wives.

(Suet, Gaius, 11)

Tiberius did nothing to correct Caligula's deviant behaviors. Indeed, the jaded old emperor seemed to take pleasure in the notion that he was "rearing a viper" for the Roman people. Not that he expected Caligula to succeed him anyway. Instead, he favored his grandson, the teenage Tiberius Gemellus, as his heir. Most of Tiberius's friends and advisors agreed that there was little chance that the emperor would allow the son of his hated rival Agrippina to follow him to power; Thrasyllus, a close confidante of Tiberius's, once even quipped that Caligula was as likely to ride a horse across the sea as he was to become emperor of Rome. But Tiberius also recognized that he was an old man who would not live much longer, and that Gemellus was still too young to reign on his own. So, in 35 CE, he named Caligula and Gemellus as joint heirs in his will. For the fate of the empire, it was a most consequential decision.

On 16 March 37 CE, Tiberius died. While many sources agree that his death was natural, others report that it may have been hurried along by Caligula and Macro, who allegedly smothered the old man with his own bedclothes. In any event, Caligula was quickly proclaimed emperor – the powerful friends he had made on Capri, including Macro and his father-in-law Silanus, had gathered the necessary support in both the Senate and in the Roman army. Thanks to their influence, the Senate disinherited Gemellus from Tiberius's will so that Caligula would not have to share power. On 28 or 29 March, Caligula entered Rome and was greeted by the Roman Senate, which hurriedly conferred on him "the absolute right to decide on everything" (quoted in Holland, 259). He therefore became the first emperor to acquire all his powers at once rather than accumulating them slowly over time.

Only 25 years old when he took power, Caligula was initially quite popular. He began his reign with an extravagant funeral for his predecessor and went on to stage numerous games and shows to the delight of the Roman people. He announced an end to the treason trials that had been a hallmark of Tiberius's regime and freed most of the political prisoners still awaiting execution. He presented himself as a public-minded ruler by abolishing unfair taxes, completing unfinished building projects, and gifting each Roman citizen 150 sesterces; heads of households received twice that amount. He tugged at the people's heartstrings by sailing to Pandateria to retrieve the ashes of his mother and brother, bringing them back to Rome for internment in the Mausoleum of Augustus. Indeed, the empire appeared to prosper for the first few months of Caligula's rule, which some ancient commentators even referred to as a golden age.

But then, with the abruptness of a lightning bolt, everything changed. Sometime around mid-October 37 CE, Caligula fell dangerously ill. It is unknown exactly what he was suffering from – some ancient sources suspect it was a nervous breakdown, while others claim epilepsy or some other life-threatening disease. For about a month, it seemed that he was on the verge of death. Macro and Silanus, afraid that they would lose their own positions if he were to die, scrambled to find a successor they could easily control. Naturally, they turned to Gemellus, who was by now 18 years old and could legally hold public office. But just as they were clearing the way for Gemellus's ascension, Caligula miraculously recovered. The emperor was horrified to learn that his closest allies had seemed to abandon him right when he was at his weakest. For a man who had been a brush away from death for most of his life, this perceived betrayal was quite unforgivable.

The first to suffer his retribution was Gemellus. Charged with treason, the unfortunate young prince was visited by two senior officials who made him drink poison. Next came Macro, the man who had probably done more than anyone else to save Caligula's life on Capri and raise him to power in Rome. At first, the emperor pretended to reward Macro by appointing him to the prestigious governorship of Egypt. But when he arrived at Ostia to take ship for his new province, Macro was arrested, stripped of his office, and forced to commit suicide. That just left Silanus, who, unlike the others, saw the writing on the wall. Aware that he had fallen from his son-in-law's favor, he went home and cut his own throat. The ease with which Caligula had dispatched his closest relatives and allies certainly disturbed many in the Senate. But unbeknownst to them, the worst was yet to come.

"But enough of the princeps," Suetonius writes partway through his biography of Caligula. "What now remains to be described is the monster" (Suet., Gaius, 22). Indeed, it seemed to the ancient writers that a switch had flipped in Caligula upon his recovery. He no longer cared about being a popular ruler but instead surrendered to his most paranoid, cruel, and depraved impulses. This was most immediately apparent in the case of Atanius Secundus, an equestrian (knight) who had foolishly pledged to fight in the gladiator arena if the gods granted Caligula a full recovery. Doubtless, Atanius had only said this to flatter the emperor, but Caligula had no patience for shameless sycophancy and forced him to honor the pledge. The hapless Atanius stood no chance against a trained gladiator and, before long, his corpse was being dragged away on a hook.

Caligula's treatment of a high-ranking man like Atanius betrayed a contempt for the whole social order. He particularly resented the Roman elite, fearful that they were always plotting against him. In 38 CE, he reinstated the very treason trials that he had abolished the year before; the political prisoners he had freed were rearrested, as were dozens of others who showed some kind of offense. Suetonius writes that Caligula had several people of honorable rank disfigured with hot irons before condemning them to the mines, or to be torn apart by wild beasts, or to be sawn in half. When an equestrian who had been thrown to the beasts loudly protested his innocence, Caligula removed him from the arena, tore out his tongue, and threw him back in. Suetonius adds that when Caligula had someone executed, it was by often means of repeated and delicate cuts so that "a man would die knowing he was being put to the blade" (Suet., Gaius, 29).

Caligula seemed to take a sadistic delight in tormenting the rich and powerful of Rome. Once, when dining with the two consuls, he suddenly burst out laughing; upon being asked what was so funny, he replied that it was just the thought that "with a single nod I could have either of your throats cut here and now!" (Suet., Gaius, 33). On another occasion, he humiliated his uncle Claudius, a senator, by having him thrown into a river. There was, of course, also the famous instance in which Caligula threatened to make his favorite racehorse Incitatus a consul. Though this has traditionally been used as evidence for the emperor's madness, it is more likely he meant it as a joke to mock the office, as if to say, 'you consuls are so useless, I might as well appoint a horse'. But the most blatant way Caligula asserted his authority over the Senate was by declaring himself a god and demanding that he be worshiped as such.

Caligula famously loved his three sisters, Agrippina the Younger, Julia Drusilla, and Julia Livilla. They had, after all, been through a lot together, surviving the destruction of their family during the dark days of Tiberius's reign. Early in his own reign, Caligula had showered them with great honors and privileges, even minting coins that portrayed them as deities. He was especially fond of Drusilla, whom he may have loved more than anyone else in his life. Indeed, some ancient sources accuse them of having had an incestuous relationship (it must be noted, however, that these rumors do not surface until decades after the fact). He married her off to his close friend, Marcus Aemelius Lepidus – the great-grandnephew and namesake of the former triumvir – with whom he was also alleged to have had a sexual relationship. In 38 CE, Caligula named Lepidus his heir, but it was really Drusilla he was entrusting the empire to. So, one can imagine Caligula's great distress when, later that same year, Drusilla died.

Too overwhelmed with grief to even attend the funeral, he instead spent his time locked away in his country villa. When he returned to Rome, Drusilla was officially declared divine, and golden statues to her were raised in the Senate House and the temple of Venus Genetrix. But even as he grieved his sister, Caligula was taking new wives. His first wife, Claudilla, had probably died in 37 CE. After her, he married two more times but divorced them each in quick succession – the first because she had remained loyal to her former husband, the second because she was infertile. Caligula's fourth marriage, to a woman named Caesonia, proved more solid. Ancient writers could not understand Caligula's infatuation with Caesonia, whom they presented as an unattractive woman with a reputation for high living and low morals. Caligula himself did not seem to understand it and once said that he felt like torturing her to figure out why he loved her so passionately. In any event, she bore him his first and only child, a daughter he named Julia Drusilla after his beloved sister.

In late 39 CE, Caligula arrived in Germany to take command of the Rhine legions. Having successfully terrorized the Senate into submission, he now sought to emulate his father by winning military victories. However, the fact that he did not know how to lead an army soon became uncomfortably apparent. When his lackluster campaign against the Germanic tribes ended in failure, he took out his frustrations by reverting to old habits – namely, accusing people of treason. He first arrested Gaetulicus, one of his generals, on charges of 'nefarious plots' and had him executed. Lepidus, too, fell under suspicion of treason and was forced to commit suicide, a rapid fall from grace for a man who had so recently been the emperor's heir and possible lover. Caligula also soured on his two surviving sisters, whom he sent into exile, before auctioning off their property. Caligula's paranoid suspicions were leaving him increasingly isolated.

In 40 CE, he secured the annexation of Mauretania, one of Rome's most important client kingdoms in North Africa. Emboldened by this success, he began planning an invasion of Britannia and even raised two fresh legions for the occasion. But for one reason or another, the invasion never materialized. Though ancient sources blame Caligula's own cowardice, it is more likely that the soldiers mutinied – the infamous story of Caligula having his men collect seashells on the beaches of the Channel could have been some form of disciplinary exercise. Nevertheless, later that year, the emperor was determined to celebrate his power. He had a mighty pontoon bridge built from the resort of Baiae across the Gulf of Naples. Over the course of a splendid two-day celebration, Caligula rode across the bridge, wearing the supposed breastplate of Alexander the Great. This was probably a grandiose response to Thrasyllus's earlier prediction that Caligula was as likely to become emperor as he was to ride across the sea.

Caligula did not only direct his cruel humor at senators. Cassius Chaerea was a member of the Praetorian Guard, a veteran of the Rhine frontier who had often been used to carry out the emperor's dirty work. Though he was a physically imposing man, Chaerea had a soft, high-pitched voice that Caligula would constantly mock as effeminate. The emperor would call Chaerea 'girl' and give him watchwords meant to insult his manliness, such as 'Venus'. One day, Chaerea had enough. On 24 January 41 CE, Caligula was passing through a side alley near his palace when he was approached by Chaerea and another Praetorian tribune, Cornelius Sabinus. As was protocol, Chaerea asked for the day's watchword. When Caligula provided an insulting one, Chaerea suddenly raised his sword and brought it down on the emperor's collarbone.

The blow was not fatal – eyes wide with shock, blood spurting from his wound, Caligula stumbled forward but was grabbed by Sabinus, who bent him over his knee. Both Praetorians continued to stab the emperor until he was dead, his body mangled beyond recognition. The assassins then cornered Caligula's wife, Caesonia, who was huddling with her daughter. Caesonia stoically accepted her fate, telling the men to "finish the last act of the drama" (quoted in Holland, 293). They did so, first by cutting her throat, then by dashing her daughter's brains out against the wall. With the death of Caligula came a ray of hope that the Roman Republic might be restored. Such hopes were quickly smothered when the Praetorians proclaimed Caligula's uncle Claudius as the next emperor – supposedly, he had been found cowering behind a curtain.

Only 28 when he was murdered, Caligula has gone down as one of history's mad rulers, his name synonymous with murderous excess and tyranny. While this reputation is certainly deserved to some extent, it is important to remember that most of those who wrote about him were from the senatorial class that he hated and had good reason to smear his name; in other words, it is best to take some facts about his cruelty with a grain of salt. Though we may never know the truth about who Caligula really was, his name and legacy loom large in the story of the Roman Empire.