Your guide to the fall of Rome and the collapse of the Roman Empire

• Your guide to the Roman empire: when it was formed, why it split and how it failed, plus its most colourful emperors

When did the cracks first begin to show in the empire?

Again, this is a heavily debated question. Many date the beginning of Rome’s end to about AD 190, when the empire started to come under attack from various tribes, including the fierce Germanic tribes known as the Goths and the Vandals.

More from our explainer series...

• What happened to the city of Babylon and the Tower of Babel
• The Great Depression – why did it happen, and how long did it last?
• The Spanish Inquisition – was it as brutal as it is popularly believed to be?

Was it purely outside factors that caused the empire's fall?

No. There are several contributing factors, some of which were taking place within the empire itself. Severe financial crisis caused by wars and overspending had led to over-taxation and inflation. This in turn saw Romans fleeing to the countryside as a way of avoiding the taxman.

• Who was Attila the Hun, the barbarian ruler who terrorised the Romans?

In addition, the empire’s expansion had slowed down considerably by the second century, meaning that the steady stream of labour provided by slaves brought in from conquered lands had also halted, causing a major labour deficit. Agricultural and commercial production declined as a result, which in turn affected trade.

Government corruption and political instability were also contributing factors to the empire’s eventual fall. A series of weak emperors from the second century had seen more than 20 men on the imperial throne in just 75 years, thanks in part to the Praetorian Guard – bodyguards to the emperor – which was using its power to decide to promote, or kill off, would-be emperors. The Senate, too, was rife with corruption and was unable, or unwilling, to rein in the excesses of its rulers. The people began to lose faith in its leaders.

• Cheese, angry gods and shoddy surgeons: the unlikely deaths of Roman emperors

Civil war also weakened the empire. The third century had seen emperor Alexander Severus murdered by his own troops while on campaign – the ensuing political instability launched the empire into a crippling civil war, which saw dozens of emperors come and go. This period of conflict was exacerbated by external threats from outside forces and continued well into the fourth century. Rome’s famous legions also began to falter, and it became increasingly difficult to recruit men to its army. Foreign mercenaries who were recruited – including the Goths and barbarians who were trying to take the Romans’ land – failed to have the same loyalty to the empire and often turned against their employers.

• After the empire: the fall of Roman Britain

What other factors are thought to have contributed to the empire's fall?

Rome’s influence was reduced significantly in the third century AD, when Emperor Diocletian took the decision to split governance of the empire: the Western Empire had its capital in Milan, while the Eastern Empire would have its capital in Byzantium, later known as Constantinople. Although the move made the empire easier to govern, the two halves drifted apart and failed to work in unison to see off external threats. The eastern half continued to grow in wealth, but the western part, which saw economic decline and continued barbarian attacks, eventually fell in the fifth century.

Some historians also cite Christianity as a factor in Rome’s fall. The religion was legalised in AD 313 and became a state religion in AD 380. Although this decree saw an end to the persecution of Christians, it also saw the decline of the Roman religion, which worshipped many gods and viewed the emperor as a divine being.

This content first appeared in the October 2017 issue of BBC History Revealed