The fall of Rome was not a single event but a gradual process spanning centuries, culminating in the deposition of the last Western emperor in 476 AD. Historians point to a convergence of political, economic, military, and cultural factors:
Frequent assassinations, civil wars, and weak emperors eroded central authority. The Praetorian Guard often auctioned the throne, leading to a revolving door of rulers who lacked legitimacy and control.
In 395 AD, Theodosius I split the empire between his sons, creating the Western and Eastern (Byzantine) Empires. The West, poorer and more exposed to invasion, could not sustain its defenses.
Rampant inflation, oppressive taxation, and a shrinking tax base crippled the economy. The reliance on slave labor stifled innovation, while trade routes were disrupted by insecurity.
Pressure from migrating groups—Visigoths, Vandals, Huns, and others—overwhelmed frontier defenses. The 410 sack of Rome by Alaric and the 455 Vandal sack were symbolic and material blows.
The army became dependent on mercenaries (foederati) with questionable loyalty. Bureaucracy grew bloated, slowing responses to crises.
Traditional Roman civic virtue waned. Christianity's rise altered loyalties from the state to the Church, while assimilation with Germanic peoples diluted Roman identity.
Britain, Gaul, Spain, and North Africa were progressively lost, shrinking the resource base needed to fund the military and administration.
In sum, Rome fell not from one cause but from a systemic failure to adapt to mounting internal and external pressures.