The “fall” of Rome was not a single cataclysm but the end‐result of many interacting pressures on the Western Empire over several centuries.  Modern scholars generally agree on a multicausal story.  Key factors include:

1. Political Instability and Corruption  
   • Frequent civil wars and usurpations—emperors often overthrown by rival generals or court factions.  
   • Weakening of central authority—power increasingly held by military commanders (praetorian prefects, magister militum).  
   • A bloated bureaucracy and patronage networks fostered graft and inefficiency.

2. Economic Troubles  
   • Heavy tax burden on landowners and small farmers, combined with widespread evasion and corruption, eroded revenues.  
   • Reliance on slave labor stifled technological innovation and small‐scale freeholding.  
   • Debasement of coinage led to chronic inflation.  
   • Disrupted trade routes (due to piracy, unrest) reduced customs and toll income.

3. Military Overstretch and Recruitment Problems  
   • The Empire’s frontiers stretched some 5,000 miles—from Britain to the Euphrates—requiring vast armies and expensive fortifications.  
   • Native Roman recruitment dwindled; dependence grew on foederati (barbarian allies settled within the Empire) and mercenaries whose loyalty could be fickle.  
   • Repeated civil wars diverted troops from frontier defense.

4. Barbarian Migrations and Invasions  
   • “Push” factors: the westward movement of the Huns displaced Gothic, Vandal, and Alanic groups into Roman borders.  
   • “Pull” factors: Rome’s wealth and (relative) stability attracted settlers and, at times, raiders.  
   • Sacking of Rome in 410 by Visigoths and in 455 by Vandals sapped imperial prestige.  
   • In 476 Odoacer, a Germanic military leader, deposed the last Western emperor, Romulus Augustulus.

5. Social and Cultural Transformations  
   • A decline in traditional Roman civic virtue and public service has been argued (Gibbon) but is hard to quantify.  
   • The rise of Christianity shifted loyalties from city‐ and emperor‐centered cults to the Church, though it also provided new social cohesion and charitable networks.  
   • Urban decay: as elites retreated to large landed estates (latifundia), many cities shrank or were abandoned.

6. Division of the Empire  
   • In 285 Diocletian formally split governance into Eastern and Western halves.  
   • The richer, more urbanized Eastern Empire (later called Byzantium) could more readily absorb shocks—tax base, manpower, established bureaucracy—while the West struggled.

7. Plagues and Environmental Strains  
   • The Antonine Plague (mid‐2nd century) and the Plague of Cyprian (3rd century) may have killed 10–25% of the population, reducing tax revenues and recruitment pools.  
   • Climate fluctuations (colder, wetter “Late Antique Little Ice Age”) possibly undermined harvests on the frontiers.

Conclusion  
No single cause “fell” Rome.  Rather, the Western Empire succumbed to a long, cumulative process in which political weakness, economic decline, social change, environmental shocks, and sustained external pressures together made imperial restoration impossible.  The Eastern (Byzantine) Empire, benefiting from a stronger economy and defensible capital at Constantinople, outlasted its western half by nearly a millennium.
