The Fall of Rome The Roman Empire in the West ceased to exist in 476 A.D., although it was gone for practical purposes many decades earlier. The proximate cause of the collapse was invasion across the Rhine and Danube Rivers by Germanic settlers. Feudalism was a system by which lords granted their vassals land in exchange for military service and personal loyalty. Although, feudalism was essentially a political and military system. Many underlying causes for the collapse have been suggested. The adoption of Christianity and preoccupation with the afterlife instead of practical matters on Earth was one. The increasing inability to administer the large empire was another. Taxes were required after the second century to support the large army and this caused unrest and revolt in the provinces.
In A.D. 340-481 a lot of stuff was happening such as battles, invasions, empires or civilizations going place to place, etc. In 378, a battle was going on that was called Adrianople.
English:
The Roman Empire in 477 AD.
Map of the "barbarian" invasions of the Roman Empi...Another battle was happening in 451 that were called Chalons. Empires and/or civilizations that were invading were Scots, Angles, Saxons, Jutes, Franks, Vandals, Visigoths, Burgundians, Lombards, Huns, and Ostrogoths. I would say the most power fullest of all is the Huns because they formed a vast empire among the nomadic steppe peoples of Eurasia and much more. The Western Roman Empire was like invaded with empires and civilizations all over the place. Invaders' attacks from every direction struck the final blow in the collapse of the Roman Empire.
As for the economy it was a mess pretty much, a lot of it changed during those years. The slave economy went into decline because slaves became sparse when conquests ceased after the second century. The empire failed to industrialized because of its dependence on slavery. Plague took a heavy toll...