Tiberius Claudius Drusus Nero Germanicus was born in Lugdunum (Lyon) in 10 BC, as the youngest son of Nero Drusus (Tiberius' brother) and of Antonia the younger (who was the daughter of Marc Antony and Octavia).
Suffering from ill-health and an alarming lack of social skills, for which most believed him mentally handicapped, he received no public office from Augustus except once being invested as an augur (an official Roman soothsayer). Under Tiberius he held no office at all.
At the assassination of Caligula in January AD 41, Claudius fled to one of the apartments of the palace and hid behind one of the curtain. He was discovered by the praetorians and taken to their camp, where the two praetorian prefects proposed him to the troops who hailed him emperor.
He was short, possessed neither natural dignity nor authority. He had a staggering walk, 'embarrassing habits', and 'indecent' laugh and when annoyed he foamed disgustingly at the mouth and his nose ran. He stammered and had a twitch. He was always ill, until he became emperor. Then his health improved marvelously, except for attacks of stomach-ache, which he said even made him think of suicide.
In history and in the accounts of ancient historians, Claudius comes as a positive mishmash of conflicting characteristics: absent-minded, hesitant, muddled, determined, cruel, intuitive, wise and dominated by his wife and his personal staff of freedmen. He was probably all of these things. His choice of women was in no doubt disastrous. But he may well have had good reason to prefer the advice of educated and trained, non-Roman executives to that of potentially suspect aristocratic senators, even if some of those executives did use their influence to their own financial advantage.
The senate's initial hesitation in granting him the throne was the source of much resentment by Claudius. Meanwhile the senator disliked him for not being their free choice of ruler.
Claudius first actions in office though marked him out as an exceptional emperor. Though he needed to for honour's sake to deal with Caligula's immediate assassins (they were sentenced to death), he did not begin a witch hunt.
In AD 42 the first revolt against his rule took place, led by the governor of Upper Illyricum, Marcus Furius Camillus Scribonianus.
Immediately after the failed rebellion of AD 42, Claudius decided to distract any attention from such challenges to his authority by organizing a campaign to invade and conquer Britain. A plan close to the army's heart, as they already once before had intended to do so under Caligula. - An attempt which had ended in a humiliating farce.
It was decided that Rome could no longer pretend that Britain did not exist, and a potentially hostile and possibly united nation just beyond the fringe of the existing empire presented a threat which could not be ignored. Also Britain was famed for its metals; most of all tin, but also gold was thought to be there. Besides, Claudius, for so long the butt of his family, wanted a piece of military glory, and here was a chance to get it.
By AD 43 the armies stood ready and all preparations for the invasion were in place. It was a formidable force, even for Roman standards. Overall command was in the hands of Aulus Plautius.
In the east Claudius also annexed the two client kingdoms of Thracia, making them into another province.
Claudius also reformed the military. The granting of Roman citizenship to auxiliaries after a service of twenty-five years was introduced by his predecessors, but it was under Claudius that it truly became a regular system.
Were most Romans naturally intent on seeing the Roman empire as a solely Italian institution, the Claudius refused to do so, allowing senators to be drawn also from Gaul. I order to do so, he revived the office of censor, which had fallen into disuse. Though such changes caused storms of xenophobia by the senate and appeared only to support accusations that the emperor preferred foreigners to proper Romans.
With the help of his freedmen advisors, Claudius reformed the financial affairs of the state and empire, creating a separate fund for the emperor's private household expenses. As almost all grain had to be imported, mainly from Africa and Egypt, Claudius offered insurances against losses on the open sea, to encourage potential importers and to build up stocks against winter times of famine. Among his extensive building projects Claudius constructed the port of Ostia (Portus), a scheme already proposed by Julius Caesar. This eased congestion on the river Tiber, but the sea currents should gradually cause the harbour to silt up, which is why today it is no longer present.
Claudius also took great care in his function as a judge, presiding over the imperial law-court. He instituted judicial reforms, creating in particular legal safeguards for the weak and defenceless.
Of the loathed freedmen at Claudius' court, the most notorious were perhaps Polybius, Narcissus, Pallas, and Felix, the brother of Pallas, who became governor of Judaea. Their rivalry did not prevent them from working in concert to their common advantage; it was virtually a public secret that honours and privileges were 'for sale' through their offices. But they were men of ability, who rendered useful service when it was in their own interest to do so, forming a sort of imperial cabinet quite independent from the Roman class system.
It was Narcissus, the emperor's minister of letters (i.e. he was the man who helped Claudius deal with all his matters of correspondence) who in AD 48 took the necessary actions when the emperor's wife Valeria Messalina and her lover Gaius Silius attempted to overthrow Claudius, when he was away at Ostia. Their intent was most likely to place the Claudius' infant son Britannicus on the throne, leaving them to rule the empire as regents.
But Narcissus was not to benefit from having saved his emperor. In fact it became the reason of his very downfall, as the emperor's next wife Agrippina the younger saw to it that the freedman Pallas, who was finance minister, soon eclipsed Narcissus' powers.
Agrippina was granted the title of Augusta, a rank no wife of an emperor had held before. And she was determined to see her twelve year old son Nero take the place of Britannicus as imperial heir.
Then on the night of the 12 to 13 October AD 54 Claudius suddenly died. His death is generally attributed to his scheming wife Agrippina who didn't care to wait for her son Nero inherit the throne and so poisoned Claudius with mushrooms.