The problem of succession gave Augustus great difficulty, his position was based on his auctoritas, his immense wealth and the political positions that the senate had given him. Under Roman law he was able to name an heir to his property but not to his political positions. Augustus wanted to ensure the stability of the political system he had created and do this he realised he needed his political successor to be in place when he died.

Bust Of Marcellus

Augustus naturally wanted to pick a successor and ideally of his own blood this was complicated as Augustus had a daughter from his marriage to Scribonia but his marriage to Livia had produced no children. His wife, Livia, however had two sons Drusus and Tiberius from her previous marriage. Augustus signified his thoughts of succession in 25BC when he married his daughter to his closest male relative, his 18 year old nephew, M. Claudius Marcellus. Marcellus soon became associated with Augustus and the higher offices of state as is evidenced in the trial of M. Primus in 23BC who engaged in an act of war outside of his assigned province in his defence he claimed he was given permission not only by Augustus but by Marcellus as well. Marcellus was made aedile in AD23 and presumably Augustus intended Marcellus to accumulate experience and to be in the position to be his natural successor.

These plans went astray when Augustus fell gravely ill in 23BC and as Marcellus was not old enough to assume the principate Augustus gave his signet ring to his oldest ally, Marcus Agrippa to signify that he should carry on his place If Augustus died. Agrippa would probably have acted as a regent until Marcellus had matured enough to step into the role of princeps. After Augustus recovered Agrippa withdrew from Rome theoretically to watch over the Eastern provinces as governor of Syria but he sent his legate to Syria while he remained at Lesbos and governed by proxy. It has been speculated that this absence was due to rivalry with Marcellus perhaps stirred up by Livia who was jealous of Agrippa's influence over Augustus.

The Ever Faithful Agrippa

Soon after Agrippa left, in 23BC, Marcellus died suddenly fuelling speculation, both modern day and ancient that Agrippa and/or Livia were implicated, this however seems more likely to be malicious gossip aimed at discrediting future emperors descended from them. Augustus did not feel there was any tar on Agrippa as he recalled him from Lesbos. Augustus began to rely more heavily on Agrippa after Marcellus's death and in 21BC he asked Agrippa to divorce his wife and marry his daughter Julia, which he did. Agrippa was now engaged in a number of campaigns for Augustus and in 18BC he obtained the extension of Agrippa’s imperium to include the senatorial provinces and had the tribunician power extended to him for five years. In 17BC Augustus adopted Agrippa’s and Julia’s two sons Gaius (born 20) and Lucius (born 17) Caesar as his own. Agrippa was now son-in-law, co-regent and heir with his two sons in the position of being his successors after him. However in 13BC Agrippa was sent to pacify Pannonia (northern Yugoslavia and Southern Hungary) and in 12BC he died there of natural causes.

Augustus was now again without a direct successor, though he had adopted Gaius and Lucius there where eight and five respectively and so Augustus now turned to Livia's son Tiberius and Drusus. Tiberius and Drusus had both been advanced rapidly, with the three year age gap between them held constant, as Augustus was so careful to do. They had been beginning to play a more important role in the Imperial government with both being used as generals in Augustus's campaigns and Tiberius holding the consulship in 13BC. They were being advanced as a second tier beneath Augustus and Agrippa.

Drusus I

Tiberius is usually thought of as the likely successor as he was forced to divorce his beloved Vipsania (Agrippa’s daughter) and marry the recently widowed Julia in 11BC, this however may have been done to tie him to the Julian family as Drusus was already married to Augustus’s niece Antonia. After Agrippa's death Augustus used both Drusus and Tiberius as his main generals in his campaigns with Tiberius fighting in Pannonia (taking over Agrippa's command) and Drusus on the Rhine. In 9BC Drusus fell from his horse while campaigning on the Rhine and died from the injuries. After Drusus’s death Tiberius was transferred to the Rhine and significantly allowed him to command the armies on his own authority rather then as a legate, presumably to allow Tiberius to earn a triumph and to increase his prestige. Tiberius continued to campaign on the Rhine and was presumably successfully by 8BC as Tiberius was awarded a triumph and made consul for 7BC. The triumph was probably more ceremonial as no great results had been made in Germany and served as recognition for Tiberius’s services while raising his profile in Rome.

Tiberius's marriage to Julia was presumably  cordial at first and Julia had a son probably in 10BC who died shortly afterwards. This marriage deteriorated badly however and Julia is famous for her infidelity. By the time Tiberius was consul Gaius and Lucius were starting to make a number of public appearances in Rome as was appropriate with their ages and the people had become accustomed to seeing them. During these years Gaius and Lucius made a number of public appearance as was appropriate with their ages and the people had become accustomed to seeing them. In 6BC the people showed their support of Gaius by electing him as consul, he was 14 and had just taken his toga virilis and legally a man. Augustus was, or at least pretended to be, very angry by this election and deferred the consulship to AD1 when Gaius would be 21. Tiberius would have been very aware that the boys growing prominence especially as Julia would have been promoting their causes.

In 6BC Tiberius was granted tribunicia potestas for five years and given a command in the East when he suddenly announced a desire to withdraw and retired to Rhodes. This is no clear indication why Tiberius did this and there is vast speculation of the reasons behind it. It is usually considered as a self imposed  banishment but may have been the result of the breakdown of his marriage with Julia and the arising jealousies as Julia promoted her sons and Tiberius wanting to avoid conflict with Gaius and Lucius. It has been suggested that Augustus may have sent Augustus as a agent in the East  as provincial governors frequently visited him and Tiberius’s return to Rome coincided with the peace settlement with Parthia in AD2. Though Augustus's claims that Tiberius had deserted him when Tiberius left for Rhodes and Tiberius’s tribunician powers were not renewed when the expired in 1BC suggest this might not be true.

Gaius Caesar

With Drusus dead and Tiberius in Rhodes Augustus now looked towards his grandsons Gaius and Lucius. In 5BC and 2BC Augustus took the consulship to introduce Gaius and then Lucius to public life, he made the boys princeps iuventutis (princeps of youth) as an introduction to leadership.

In 2BC Augustus received a blow when Julia was accused of having dozens of lovers, either through boredom or as a protest as being used as a political pawn. There is even a suggestion that she was part of a plot to presumably replace her father with her sons Gaius and Lucius. This idea has been arrived at as a number of her lovers, who were of reasonable prominence, were executed and Augustus's subsequent appointment of two praetorian prefects later in this year stemming from a need for greater security. Julia was banished to the desert island of Pandateria and even Tiberius tried to intercede on her behalf (though he did also officially divorce her) but Augustus would only relent to the extent to permit her to move to Rhegium. Her mother Scribonia accompanied her on this exile. This event while embarrassing to Augustus also caused some doubt of the parentage of Julia and Agrippa's children and may have been detrimental to the claims of Gaius and Lucius.

Gaius and Lucius however were steadily becoming more important and beginning to take over a number of duties from Augustus. In 1BC Gaius was sent to negotiate with Parthia and his consulship was set for AD1. A letter from Augustus to Gaius has survived describes how Augustus sees his two sons taking over from him and he describes this in a very positive manner. As for Tiberius and Drusus, Augustus kept the three year age gap between Gaius and Lucius in tact and he sent Lucius to a command in Spain in AD2. Unfortunately he never arrived as he died with a fever on route.

A Young Tiberius

Tiberius had tired of Rhodes and he had repeatedly petitioned to be allowed to return to Rome, Augustus finally relented in AD2 (but before the death of Lucius), probably under heavy pressure from Livia. Tiberius was not given a public office to hold and appears to have returned as a private citizen. In AD3 however Gaius was wounded in a battle and this appears to have affected him badly as he requested to retire, this became academic as he died in AD4.  

Augustus was now again without a successor. After a period of negotiation, in June of AD4 Augustus adopted Tiberius and obtained a 10 year grant of tribunician power for him as well as a grant of imperium for the provinces. Augustus also adopted Agrippa and Julia’s final son, Agrippa Postumus (he was born after Agrippa died) and made Tiberius adopt Germanicus, his brother Drusus's son, who had blood of Augustus’ family through his grandmother Octavia (Tiberius had a son Drusus himself who was slightly younger then Germanicus). It is thought Augustus was creating another two tier system of brothers with the immediate successors of Agrippa Postumus and Tiberius and then next generation of Germanicus and Drusus. Agrippa Postumus however did not have the same character as his brothers and by AD7 Augustus disinherited him and exiled him to a desert island, leaving Tiberius as his only realistic heir.

Over the following years Tiberius served as co-regent as Augustus got older and frailer. In AD13 when Tiberius tribunician powers and imperium was renewed along with Augustus’ it is clear he was Augustus’ equal partner. Augustus died in AD14 and Tiberius was already in place and the smooth succession Augustus had planned automatically took place.