Claudius (10 BCE to 54 CE) was the fourth Roman emperor, who reigned from 41 to 54 CE. Though a member of the imperial Julio-Claudian Dynasty, his rise to power had always seemed unlikely. Indeed, for much of his life, he had been ostracized by his own family due to his disabilities. But after the assassination of his nephew, Caligula, in 41 CE, he was proclaimed emperor by the Praetorian Guard. His reign was a relatively prosperous time for the Roman Empire, seeing the construction of new roads and aqueducts, as well as the conquest of Britain. He died in 54 CE – possibly poisoned by his wife – and was succeeded by his adopted son Nero (reign 54 to 68).

Claudius was born Tiberius Claudius Drusus on 1 August 10 BCE in Lugdunum in Roman Gaul (modern Lyon, France). He was the youngest surviving child of Nero Claudius Drusus (also known as Drusus the Elder), a popular Roman general and brother of the future emperor Tiberius. His mother, Antonia Minor, was also of high pedigree, being the daughter of Mark Antony and Octavia Minor; through his grandmother Octavia, Claudius was also a great-nephew of the first Roman emperor, Augustus. When Claudius was barely a year old, his father died in a riding accident while leading soldiers in Germany. Drusus's death came as a shock to the whole empire, and the military camp where he died was viewed as 'accursed' ever since. Claudius was thereafter raised by his mother, who never remarried.

From an early age, it was clear that Claudius suffered from some kind of disability. But far from being an understanding and loving parent, Antonia constantly belittled her son for his perceived defects. According to the historian Suetonius, she referred to him as a monster who had been "begun by Nature but only half-fashioned," and, when accusing anyone else of stupidity, would say that they were "being a bigger fool than her son Claudius" (Suet., Life of Claudius, 3). Though Emperor Augustus was kinder to his great-nephew, he was determined to keep the boy hidden from public view, writing:

If, on the other hand, we feel him to be – as the Greeks might put it – a moron… then we must on no account give the kind of people who jeer and laugh at such things the chance to make him (and us!) objects of mockery.

(Suet, Claudius, 4)

As Claudius grew older, his disabilities became more pronounced. He walked with a limp, spoke with a stutter, and was constantly twitching. He was prone to drooling, and his nose ran when he got excited. Scholars are uncertain exactly what disability he suffered from – traditionally, polio has been suggested, though modern scholarship posits that it was more likely some form of cerebral palsy or Tourette's syndrome. In any case, Claudius was hidden away for much of his youth and was prevented from embarking on the cursus honorum, the 'career ladder' of public offices that any aspiring Roman politician was expected to climb.

This must have been particularly frustrating for Claudius, who had to watch his older brother Germanicus win glorious military victories along the Rhine frontier and be celebrated throughout the Roman world. When Augustus died in 14 CE, Claudius appealed to his uncle, the new emperor Tiberius (reign 14 to 37 CE), to grant him a public office. But Tiberius, too, considered Claudius an imbecile, and granted him consular ornaments but nothing of any substance. By then, Claudius was 23, an age when most of his peers had already entered public life. He must have felt destined to languish in obscurity.

Though he was despised by his family, Claudius seems to have been well-liked by others. The equestrian class (knights) had selected him to lead their delegation to Augustus's funeral. When his house burned down, the Roman Senate voted to rebuild it at public expense and even agreed to let him debate in the Senate House (both motions were vetoed by Tiberius). After Germanicus's premature death in 19 CE, there was even talk that Claudius might assume his late brother's role as heir apparent to the Roman Empire.

But this came at a time when the power-hungry prefect of the Praetorian Guard, Lucius Aelius Sejanus, was conducting his bloody treason trials. Hoping to avoid catching Sejanus's jealous attention, Claudius distanced himself from the conversation about the succession and increasingly withdrew into private life. As the years passed, he contented himself with scholarship, with a particular interest in the study of history. Even after Sejanus's downfall and execution in 31 CE, Claudius continued to keep to himself.

In March 37 CE, Tiberius died, and Claudius's 25-year-old nephew, Caligula (reign 37 to 41), came to power. In the first months of his reign, Caligula was eager to court the popularity of the masses and, as part of his public relations campaign, he appointed Claudius to the prestigious office of consul; this was done to honor the memory of Claudius's brother, Germancius, who was still beloved by the people. At first, Claudius relished this new role and the respect that came with it. According to Suetonius, when he first entered the Roman Forum as consul, an eagle landed on his left shoulder, a sign of the gods' favor. Sometimes, when Caligula was absent from Rome, Claudius would preside over the gladiatorial games and chariot races, where he would be loudly cheered.

But this newfound respect proved all too fleeting. As his reign progressed, Caligula became increasingly sadistic and often found pleasure in tormenting those around him, including his uncle. He frequently humiliated Claudius before the Senate and once even pushed him fully clothed into a river. Other senators took this as a sign to bully Claudius as well. Suetonius writes:

All he had to do was turn up a few minutes late for supper, and he would have to make an entire tour of the dining room before someone would grudgingly make space for him; likewise, should he ever doze off after dinner – something he was quite prone to doing – he would be pelted with olive and date stones, and on occasion a joker might lash him with a rod or a whip ('just for the banter' was the excuse).

(Suet, Claudius, 8)

The Roman historian Cassius Dio adds that Claudius was so stressed by this constant humiliation that he became sickly and quickly lost weight. But then, on 24 January 41 CE, everything changed. Two disaffected members of the Praetorian Guard, Cassius Chaerea and Cornelius Sabinus, assassinated Caligula in a side alley near the palace. Not satisfied with merely killing the emperor, the Praetorians went on to murder Caligula's wife and infant daughter – indeed, it seemed as if they meant to wipe out the entire imperial family. According to the official version of events, Claudius heard what had happened and feared that Caligula's assassins meant to kill him too. He hid behind a curtain but was soon discovered by a Praetorian named Gratus. When the quivering Claudius sank to his knees, expecting to be struck, Gratus raised him to his feet and proclaimed him emperor. Claudius was then whisked away to the Praetorian camp for his protection.

Such, at least, was the story that was presented to the Senate. In the immediate aftermath of Caligula's assassination, some senators were hopeful that the days of autocratic, one-man rule were over, and that the republic might now be restored. These hopes were soon crushed when it was revealed that Claudius had taken sanctuary with the Praetorians and had been proclaimed emperor, that he had secured his position by showering the Roman army with bribes. By claiming to have been found cowering behind a curtain, Claudius was presenting himself as a reluctant ruler, one who had been quite literally dragged kicking and screaming to power. In contrast to the egomania of Caligula, it harkened back to the soft power of Augustus's rule and was much harder to deny. Before long, the people were chanting his name, and it became clear that Claudius was firmly in charge, and that the days of the old Roman Republic were lost forever.

In securing his position, Claudius assured the Senate that he was not as bloodthirsty as his predecessor. True, he executed Chaerea and forced Sabinus to commit suicide – it would have set a bad precedent to let Caligula's assassins live – but he largely turned a blind eye to the senators who had been suspected of conspiring with them to restore the republic. He knew how important it was to placate the senatorial class, and often attended Senate meetings, sitting in between the consuls and waiting for his turn to speak like anyone else. He refused some of the most grandiose titles and honorifics granted to his predecessors, like imperator, and allowed the Senate to mint its own bronze coinage for the first time in decades. Despite this attempt to foment goodwill, he did have to deal with several plots against his rule. The general Appius Silanus was executed early in Claudius's reign, probably after a coup attempt. He would not be the last to die – Suetonius claims that Claudius executed 35 senators and 300 equestrians during his reign. In the end, his rule was not as bloodless as he had first promised.

Once he had consolidated power through this mix of bribery, executions, and placating the Senate, Claudius could turn to the difficulties of administration. He established a secretariat and entrusted the positions to loyal former slaves. Gaius Callistus, who had risen to prominence as an advisor to Caligula, stayed on as Claudius's secretary of justice. Pallas, who had been owned by Claudius's mother before gaining his freedom, was secretary of the treasury. But the most important of these men was Narcissus, who had been Claudius's own slave before becoming secretary of correspondence. These freedmen wielded great power – indeed, it was Narcissus who convinced Claudius to execute Silanus, after dreaming of the general's treachery. Additionally, the freedmen were entrusted to speak with the emperor's voice. In one notable instance, Narcissus addressed the Roman legions before the invasion of Britain, talking them down from mutiny. Though many senators whispered that these freedmen were manipulating the emperor, their unlikely rise mirrored Claudius's own.

The best way for Claudius to secure his power was to orchestrate a grand military campaign, one that would rival the exploits of any of his predecessors. For his target, he chose Britain, a land perceived as mysterious and barbarous, which had been briefly invaded by Julius Caesar a century before but had otherwise escaped the domineering hand of Roman rule. In 43 CE, the time for another invasion seemed ripe; the kingdoms of southern Britain were being torn apart by a series of dynastic squabbles, while various Roman legions were already assembled near the Channel. That summer, Claudius dispatched the general Aulus Plautius to Britain at the head of four legions.

The invasion was a success. After two battles, the Britons were defeated; while resistance would continue in the north, the Romans were able to establish a foothold and added another province, Britannia, to the empire. Claudius himself would visit Britain for 16 days, and, upon his return to Rome, he was treated as a conquering hero. He was granted a Roman triumph, riding through the streets in a ceremonial chariot with his wife, Valeria Messalina, by his side. The Senate even awarded his two-year-old son the name 'Britannicus' to honor the victory. In 50 CE, the British general Caractacus was captured. Rather than have him executed, Claudius acknowledged Caractacus's valor by granting him clemency and allowing him to live out his remaining days on land provided by the Roman state.

Claudius also sought to cement his legacy by implementing public works projects, not only in Rome but also throughout the provinces. He built two aqueducts, the Aqua Claudia and the Aqua Anio Novus, which ensured the flow of fresh water into the heart of Rome. He restored the port at Ostia, at the mouth of the Tiber, so that grain shipments could more easily be transported up the river and into the capital.

He built roads and canals for easier transportation throughout the empire and drained Fucine Lake to provide more arable lands for the farmers in Italy. All these construction projects offered plenty of opportunities for employment. The Fucine Lake project alone required 30,000 laborers over the course of 11 years. This served to make Claudius quite popular with the masses. When the people of Rome heard that he had been killed on the road to Ostia, they began to riot and only calmed down once his safe return to the city proved the rumor false.

While Claudius's reign was certainly prosperous for the empire at large, it was also beset by its fair share of palace intrigue. In 41 CE, Claudius had invited his two nieces, Agrippina the Younger and Julia Livilla, back from exile, where they had initially been sent by Caligula. Apparently, Claudius became fond of the beautiful Livilla and spent a lot of time in her company, arousing the jealousy of his (third) wife, Messalina. Clearly fearing for her own position, Messalina brought charges of adultery against Livilla and pressured Claudius into banishing her once more. This time, the hapless Livilla would never return, starving to death only a few months later.

But despite being the wife of the emperor, Messalina herself was not immune to falling victim to a similar scandal. It had long been rumored that she was a nymphomaniac, prone to cheating on her husband with various men; indeed, according to an improbable story told by the historian Tacitus, she once competed with a prostitute to see who could sleep with more men in a single night (Messalina, of course, came out on top). But she outdid all these rumors in 48 CE when she married her lover Gaius Silius in a public ceremony in Rome while Claudius was away supervising the construction at Ostia. Scholars are still unsure whether she divorced Claudius first before marrying Silius, or whether this was part of a larger coup.

In any event, Claudius was ironically informed of Messalina's marital betrayal by one of his own concubines. He was then convinced by Narcissus that the marriage was part of an attempt to overthrow him – indeed, Narcissus had long opposed Messalina in court politics and was undoubtedly happy to ensure her downfall. Egged on by Narcissus, Claudius reacted swiftly. Silius was arrested and executed, as were several of his friends suspected of conspiring with him (not even the popular actor Mnester escaped the emperor's fury; accused of sleeping with Messalina, he was beheaded despite his hysterical protests).

Messalina herself was approached by an officer of the Praetorian Guard and instructed to commit suicide. When she found that she was unable to do it, one of the guards drew his own sword and killed her. According to the ancient sources, her execution was ordered by Narcissus, who had been pretending to act on the emperor's orders. When Claudius learned of Messalina's death for the first time, he showed no reaction but merely asked for another cup of wine.

After Messalina's death, Claudius went in search of a new wife. By this time, he was painfully aware of the weakness of his position – though he was a distant relative of Augustus, he was not a direct descendant, a fact that his opponents could use to paint him as illegitimate. Additionally, he was growing old, and his only son, Britannicus, was still a boy and was not ready to take on the role of emperor. Likely for these reasons, Claudius decided to marry his niece, Agrippina the Younger; not only was she a direct great-granddaughter of Augustus, but her son, Lucius Domitius Ahenobarbus, was already a popular boy whose pedigree would probably be more palatable to the Senate than that of Britannicus whose own mother had died in disgrace.

Claudius married Agrippina despite the traditional Roman disdain for incest; indeed, he had to overturn a law that forbade uncles from marrying their nieces. Once this was done, he formally adopted Agrippina's son, who was given the fancy new name of Nero Claudius Caesar. Nero was quickly married off to Claudius's daughter Octavia and was officially made joint heir with Britannicus. As Nero rose in the line of succession, however, Britannicus found himself increasingly sidelined. Although he had the support of Narcissus, he was unable to compete with his older stepbrother, who was already giving speeches before the Senate at the age of 16. Claudius himself was unconcerned, believing that Britannicus would have his moment when he came of age.

But then, on 13 October 54 CE, Claudius suddenly fell ill and died at the age of 63. At his funeral, he was deified by Nero and the Senate. His death was presented as natural, which it very well may have been. After all, Rome had been afflicted by fever all that year, and the emperor had always been sickly. But most ancient sources whispered that he had really been murdered, with most of them pointing the finger at Agrippina. It was, of course, suspicious that Claudius had only fallen ill when his most powerful supporter, Narcissus, was out of the city. Her motive would have been simple – get Claudius out of the way to ensure her son's swift rise to power.

This theory seems to have been supported by Nero himself, who once joked that mushrooms were the food of the gods since "it was by the means of a mushroom that Claudius has become a god" (quoted in Holland, 343). This seemed to imply, of course, that Claudius had died from a poisoned mushroom. In any case, Nero and his mother quickly moved to consolidate power, having both Narcissus and the teenage Britannicus killed. Aside from his conquest of Britain, Claudius is probably best remembered today for allowing the rise of Nero, the man who would bring about the destruction of the Julio-Claudian Dynasty