Tiberius was left with no male heir in the years directly before his death. He therefore took Germanicus' son Gaius into his palace and cultivated the youth. Upon Tiberius' death in 37, the Praetorian Prefect Macro, an acquaintance and ally of Gaius, proclaimed the latter as Princeps, and the Senate ratified the choice. Gaius was better known as Caligula, meaning 'little boots'. He had been taken by his father Germanicus on his several German campaigns, and had been equipped with miniature roman centurion's uniform, complete with little boots. Hence the nickname, which stuck. His rule begins the Julio-Claudian dynasty, all of whose members were descended by blood from Augustus (related himself to Julius Caesar), or to the latter's third wife Livia (previously married to T. Claudius Nero). Caligula began his rule well: he stopped the rash of treason trials, recalled political exiles, gave shows for the Roman populace, and brought his uncle Claudia, despised son of Antonia, into the political arena. In October of 37, though, Caligula became nearly fatally ill, and when he recovered, became a pathological monster.
In order for the Principate to function well, cooperation with the Senate was necessary. Caligula was not interested. He beat one consul over the head with a chair, and threatened to install as senator Incitatus—his horse. Offending the Rome aristocracy even more, he dressed as the gods in public, and even engaged in the games himself, as charioteer, gladiator, and singer. He proceeded to build a temple to his own divinity and engage in incest with his sister Drusilla. In 39, there was a conspiracy against him in the Rhine area legions. He killed the conspirators and then led the army into battle over the Rhine. Though the campaigns were marginally successful, those 'captured' Germans present at his triumph were in actuality Romans in disguise. Caligula then spent the winter in Gaul, readying his forces to cross over to Britain for a conquest. When they arrived to the channel in the summer, however, the legions were ordered simply to collect seashells.
This insanity was topped off by his most self-destructive craziness. Judaea had been a client kingdom since Pompei. Herod had been the last important king there. A Hellenized Jewish convert from Transjordan, Herod had been a friend of the Romans, and built great structures all over the kingdom. He had died in 4 BCE, dividing up the realm among his three sons, giving the core Judaean lands to his son Archilaus. Archilaus' rule was so poor and impious that the Jews petitioned Augustus to annex the area. In 6 CE Judaea was thus made a Roman province, ruled by an imperial procurature from Caesaria, a non-Jewish town. Back in Caesar's time, the Jews of Alexandria had supported him, so the dictator had accorded them certain privileges: they had religious freedom and could keep the Sabbath; they were not liable for military service; the taxes that went to the Temple in Jerusalem would not be diverted to the state fisc; and in Judaea itself, Roman coins would not contain the Emperor's likeness, out of respect to the Jewish ban on graven images. In the same vein, Jews were not required to participate in the imperial cult (deification). Here, Caligula erred. Alexandrian Greeks had resented the Jews' exemptions, and demanded that Caligula's statue be emplaced in the Jews' Temple in Jerusalem. Riots broke out in support of this in Alexandria, and Caligula, who was engaged in propagating his own divinity in any event, took over the notion, and commanded that his likeness—tantamount to an idol—be put in the Temple. Herod Agrippa, one of Herod's descendants, told him he was crazy, but Caligula commanded the Syrian governor to comply. The latter stalled, upon which Caligula threatened to kill him. In the event, the stature never arrived, because in 41 Caligula was assassinated by an officer of the Praetorian Guard whom the emperor had offended.
With no obvious successor, a political vacuum emerged. In chaotic circumstances, the Senate met to decide the fate of the Empire. There was talk of return to a dual consul republic, and some thought to choose the Princeps. In the meantime, Praetorian Guard members had discovered Claudius, Germanicus' younger brother, cowering behind a curtain in the palace. Taking him to the Praetorian camp, the Guard recognized him as emperor, with financial inducement. Though the Senate balked at first, Herod Agrippa interceded and negotiated senatorial recognition of the new Princeps.
Claudia was at first glance an unlikely choice, and was not viewed as suitable by the Roman elites. He was already fifty, had no administrative or military career, and suffered from physical defects such as weak legs and a lolling head. His mother had hated him and the rest of his family had not considered him Princeps material. Still, he was not without merits. Augustus had seen he was smart, and had spent late nights talking to him over drinks. Claudius was also an historian. He had written about Carthage, and he had also produced a forty- one-volume history of Augustus. Thus, he knew all about the Empire, its history, and how to administrate it. He was interested in governmental efficiency. Given this inclination and his deformities, it was no wonder that the Senate disliked him. Though he was not hostile to it as a body, he did revive the sensor to eliminate bad senators from the ranks, and abolished a number of senatorial offices duplicating imperial ones. He also installed larger numbers of equestrian procurators in senatorial provinces, reducing financial powers of senatorial quaestors. At times he interfered with proconsular appointments, and wrested control of the aerarium, the main Roman treasury. Thus, while all of this contributed to a greater administrative and policy efficiency, it incurred aristocratic ire as it dimmed the Senate's power.
Claudius proceeded to create a thoroughgoing Roman bureaucracy. While Augustus had been responsible for administrative changes, his rule had been exceedingly personal. The Princeps had himself to manage all matters, yet by the 40s and 50s, the amount of administrative matters was becoming too much for one person to handle. Claudius thus founded secretariats with Roman freedmen as their staff: 1) Narcissus handled imperial correspondence; 2) Palas oversaw finances; 3) Callistus handled petitions and judicial matters, while 4) Polybius' duties are unclear to us. Each of these was a quasi-minister with miniature ministries, and the secretaries themselves became rich and powerful, wielding influence over the Princeps himself. At the same time, the secretariats' existence aggravated Claudius-Senate relations. An additional role Claudius undertook regarded public works. A new harbor at Ostia was built, just as was constructed a Roman road from the Adriatic to the Danube. He also cared for the provinces, using the imperial procurators to monitor the (senatorial) quaestors.