The rise and fall of the Roman Empire

Octavian, the adopted son and grand nephew of Julius Caesar, emerged victorious after a series of civil wars by 31 BC.

Octavian made a public display of relinquishing his powers back to the Senate, including his position as triumvir and his absolute dictatorship.
The Senate, in turn, granted him power voluntarily, but in different forms, cloaking absolute power in republican institutions.

Octavian was given the title Augustus, implying greatness, venerability, and even divine status, though without any explicit political meaning.
The Senate granted him legitimate republican powers, including:
- Consulship (elected as consul or serving as proconsul)
- Power of the tribunate (veto power)
- Title of imperator (commander of the army), allowing him to control most of the legions and provinces.

Augustus held real power all along, and the Senate was aware of this, fearing renewed civil war if they tried to remove him.
Augustus and the Senate worked together to consolidate power in a way that didn't appear dictatorial to the public.
The people saw Augustus as the savior and restorer of the republic, leading them into a golden age.

Augustus ruled with humility and deference for the Senate and republican forms, unlike Julius Caesar.
His rule, though essentially a military dictatorship, was couched in republicanism, seemingly fooling everyone.
His long reign established the position of emperor as a necessity, even though they didn't consider it a monarchy.

Augustus, not having a son, passed on the position through adoption to his stepson, establishing the Julio-Claudian dynasty.
Other than Augustus, the Julio-Claudian emperors (like Nero) were not considered great, often struggling with mental illness.
The Julio-Claudian dynasty ended with Nero in 68 AD, leading to another round of civil war.

The civil war following Nero's death was won by Vespasian, establishing the Flavian dynasty.
This dynasty saw the first father-to-son succession, initially restoring the Augustan form of emperor as leader of the senate.
Vespasian's second son, Domitian, became more authoritarian, leading to his assassination in 96 AD.

The period of the Five Good Emperors was characterized by:
- Good relationships with the Senate (except for Hadrian, who avoided them)
- Maintaining peace
- Maintaining the respect of the army
- Keeping enemies at bay
Notably, none of the five good emperors, except the last one, came to power through blood succession, but instead through adoption and grooming of a successor based on merit.
This formula led to a long period of stable and effective rule.

Hadrian, Trajan's successor, decided that the empire had expanded far enough and focused on fortifying its borders.
He shifted the Roman mentality from offensive expansion to defensive consolidation, marking clear distinctions between Roman and barbarian territories.
Hadrian built fortifications like Hadrian's Wall in Britain to delineate the Roman Empire's boundaries.

Marcus Aurelius, the last of the five good emperors, reigned from 161 to 180 AD.
He spent much of his reign at war against Germanic tribes and other groups and faced a plague that devastated the army.
His actions maintained stability but his son, Commodus, proved to be a terrible emperor, losing territorial gains and bankrupting Rome.
Commodus was murdered in 192 AD, leading to another round of civil war.

Septimius Severus won the civil war and founded the Severan dynasty.
The Severan dynasty marked a turning point in the Roman Empire, shifting away from the Augustan compromise of republicanism and toward a true monarchy.

Exclusion of the Senate from power.
Military commands given to non-senators.
Separation of civic and military responsibilities.
Reliance on the military for power and ignoring the senate.
Septimius Severus's dying advice to his sons: "Get along with each other, pay the army well, and to hell with everyone else."

The Severans weakened the Parthian Empire, leading to the rise of the Sassanid Persians, a more formidable enemy.
The Sassanid Persians sought to reclaim territories including Syria, Asia Minor, and Egypt.
The Severans diluted the currency, causing inflation.

Emperor Diocletian (284-305 AD) ended the Third-Century Crisis by dividing power through the tetrarchy, the rule of four.
The tetrarchy consisted of two senior emperors (Augusti) and two junior emperors (Caesars), ruling together as an imperial council.
This system allowed generals to defend the frontier without the temptation to seize power, because they already held it.

After Diocletian's retirement, the tetrarchy fell apart due to civil war.
The empire became divided between East and West.
Emperor Constantine won the war in the West by 312 AD and later took control of the East.

Constantine converted to Christianity, bringing the previously persecuted religion to power.
Emperor Theodosius later made Christianity the official state religion of the Roman Empire.
Constantine built a new capital city at Constantinople, shifting the empire's center of power from West to East.
The Eastern Roman Empire, later known as the Byzantine Empire, survived, while the West declined.

After Constantine's death in 337 AD, the Western Roman Empire declined due to:
- Internal division and civil wars
- Declining army
- Declining economy
- External pressure from Germanic tribes displaced by the Huns.

The Western Roman Empire faced a full-scale migration of Germanic peoples fleeing the Huns.
The refugees, who were skilled warriors, strained Rome's resources.
In 378 AD, at the Battle of Adrianople, a Roman emperor was killed fighting a Germanic tribe within the empire.

Theodosius (379-395 AD) was the last Roman emperor to rule over the entire empire.
He made Christianity the official state religion and subdued the Germanic tribes within Rome.
However, the tribes submitted to him personally, not to Rome, foreshadowing future problems.

Upon Theodosius's death in 395 AD, the empire divided permanently into East and West.
The Eastern Roman Empire (Byzantine Empire) survived until 1453, while the Western Roman Empire fell in 476 AD.
The migration of Germanic tribes and the collapse of political authority led to the rise of religious authority in the West, with the Pope becoming more influential.