In 117 AD, the Roman Empire reached its greatest geographic extent, spanning 5 million square kilometres and enjoying unprecendented economic and cultural supremacy across Europe, Africa and Asia.
Its vast population was enjoying the spoils of trade from across the known world, spectacular civic projects and the protection of one of the most effective armies the world had ever seen.
But the collapse of the empire was not far away.
Political confusion at the highest level was increasingly common, with five different claimants for the throne in 193 AD alone.
Economic strife grew, with emperors unable to deal with high inflation, and the colossal financial strain of maintaining the army.
By 226 AD the growing strength of the Sassanid Empire in Persia was a threat in the east.
It began to attack the Romans, forcing successive emperors to move large portions of their military to the eastern part of the empire.
After nearly a century of war, and some significant territory losses, Rome made an uneasy peace with the Sassanid Empire in 299 AD.
But the impact of this campaign was significant. In 235 AD Emperor Alexander Severus had been deposed as a direct result of his focus on the Sassanid threat, instead of that from German barbarians.
This had begun a period of internal crisis, as prominent generals started civil wars to try and wrest control of the empire from each other.
The protracted conflict was also expensive, and lower tax revenue due to a continually debased currency meant it could not be shared among everyone. In the end, the army got the bulk of it.
Provincial towns attempted to continue major building works, but it quickly became clear that this was not possible with the reduced revenue.
Even when they reduced that ambition to only repairing and maintaining their current buildings, towns struggled to support their large populations.
As a result, over the course of decades, people began to leave the cities to practise subsistence agriculture, further stripping the empire of its income, and the cities of their population.
Diocletian, the emperor to end the war with the Sassanid Empire, brought some stability. He split the Roman Empire into four parts, with four rulers, to create the Tetrarchy.
He resigned 21 years later, anticipating that his major changes to how the empire operated were enough to ensure that Rome would survive.
But his attempted economic reforms, particularly price controls, did little to slow inflation.
Cities across the empire started to limit their involvement with the empire, operating independently, and lowering the taxes they sent to the government.
These financial struggles meant spending on the Roman army, which had succeeded based on its dedication to a discipline and uniformity, was becoming harder to justify.
It meant the army was now comprised mainly of conquered and allied tribes instead of trained Legionaries, and it became increasingly disorderly.
The loyalty of troops to the emperor was replaced with loyalty to individual generals.
Tribes providing troops, from both within the empire and outside it, had significantly enhanced their military ability and economic freedom simply due to their proximity to the Romans.
At this point, overall control was breaking down as regional leaders were fighting with each other.
Income inequality was at an all-time high, leading the regional poor to further turn their back on the empire.
Corruption had always been endemic but now tax revenues were lower than ever. This lack of funds forced the empire to reduce the size of the army, leaving the military completely ineffective.
Civil wars began again, with emperors being deposed regularly, while the loyalty felt to individual generals allowed them to use their armies to fight for their own interests.
The barbarians of Germany were now faced with a threat even further east, the Huns, so began to press into Roman territory.
The combination of a more effective barbarian fighting force, and an empire weakened from the inside, meant they were able to transform Roman territories into independent cities.
Finally, in 395 AD, the empire was forced to split for good, with the West casting the East aside for it to survive on it's own.
But the barbarians continued into Roman territory, and in 410 AD the Vandal Alaric led a horde into Italia, eventually sacking Rome itself.
Britannia, and large parts of Hispania and Gaul were lost to Gothic control within 15 years. The Huns were also appearing in some northern areas.
At this point, the lack of control and long-distance adminstration options meant large operations failed repeatedly - Africa, Carthage, more of Gaul and German territories were all lost over the next three decades.
In the last years of the empire, emperors were little more than puppets, agreeing to the demands of German warlords under threat from their much larger armies.
So finally, by 480 AD, the Western Roman Empire had ended, and new rulers were solidifying control across Western Europe.
Note: This is one interpretation of events - there are many. This version primarily uses Peter Heather's, The Fall of the Roman Empire (2005) and Bryan Ward-Perkins's The Fall of Rome and the End of Civilization (2005).