The fall of the Roman Empire is a complex historical event attributed to multiple interrelated internal and external factors, occurring over several centuries, with historians often marking 476 AD as its endpoint when Emperor Romulus Augustulus was deposed by the Germanic chieftain Odoacer. Here are some of the major causes commonly cited:

1. **Political Instability**: The Roman Empire faced severe administrative and political challenges, including frequent changes in leadership and civil wars. Over the 3rd century AD, it is estimated that Rome had more than 20 emperors, many of whom came to power by violent means and lasted briefly. This undermined the stability and effectiveness of the government.

2. **Economic Decline**: Several economic factors contributed to the collapse. Heavy taxation was needed to support the empire's military and bureaucracy, but it stifled economic growth. Widespread corruption and inefficiency in tax collection reduced state revenue. The economy also suffered from reliance on slave labor, which stifled technological advancement and reduced incentives for innovation.

3. **Military Overstretch**: At its height, the Roman Empire spanned a vast territory, which required a huge military commitment to defend. The constant need for troops led to overstretched resources. Additionally, as the frontiers expanded, maintaining and protecting the boundary of the empire became increasingly difficult and costly.

4. **Barbarian Invasions and Pressures**: The migration and invasion of various tribes such as the Goths, Vandals, Huns, and eventually the Franks into Roman territory significantly strained Roman military resources. These groups applied military pressure and sometimes settled within the boundaries of the empire, gradually eroding Roman control and influencing the local Romanized populations.

5. **Decline in Civic Virtue and Morale**: Many Roman historians, such as Livy and later Edward Gibbon in his analysis, have argued that a decline in civic virtue—responsible citizenship such as public service and military duty—contributed to the fall. This decline in morale and duty was often attributed to an increase in luxury and the decay of traditional Roman values.

6. **Administrative Division**: Emperor Diocletian (r. 284-305 AD) divided the empire into the Western and Eastern Roman Empires in an attempt to make governance more manageable. While this initially helped in administration, it eventually led to divergent interests and weakened the western part, making it more susceptible to external pressures.

7. **Religious Changes**: The spread of Christianity and the eventual adoption of it as a state religion under Emperor Constantine changed the cultural and religious landscape of the empire. Some scholars argue that this undermined traditional Roman values and unity, although others see the new religion as providing a unifying force among diverse populations.

8. **Environmental and Health Factors**: There were also environmental factors such as climate change, agricultural decline, and plagues (notably the Plague of Cyprian and later the Justinian Plague) which weakened the empire by reducing population, workforce, and economic output.

Ultimately, the "fall" of Rome wasn't an event but a process. The Eastern Roman Empire, or Byzantine Empire, continued until 1453 AD when it fell to the Ottoman Turks. The disintegration of the Western Roman Empire led to the development of feudal kingdoms and eventually the modern nations of Europe. Each cause interwove with others, creating a complex tapestry of events that led to one of history’s most significant transitions.
