The Roman Empire collapsed of its own corruption and internal dissatisfaction- external enemies were a minimal factor. Roman Empire stood in Great power for many decades, undefeated, strong and dominant. It was a common belief that the empire would last eternally. During the rule of Augustus, it was a time of the cultural development, piece and economic stability. It was the Golden age as historians call it. Yet nothing lasts forever. After the death of Augustus came the Five Good emperors, under whose rule the empire still flourished although not as much as under Augustus. I disagree with the statement above, I think Roman Empire declined due to external attacks of barbarians, which proceeded through the years and damaged and weakened the Roman Empire, rather then due to internal corruption .
Although the decline of the Roman Empire was a great deal related to bad rulers and the chaos that occurred in the empire after the death of Marcus Aurelius, the last good emperor. His son, Commodus(r. 180-192) came to power. He was incompetent and oppressive, and was not capable to rule. Commodus was assassinated and after the civil war exploded, three emperors rule in swift succession. In the third century Barbarian invasions became severe. The Parthians made the Iranians independent, which gave them the right to establish independent empire.
Roman Empire could not let the threat of the raising powers exist, Romans finally conquered Iranians in 198 c.e. by reaching and destroying their capital. In 24 BCE Iranian dynasty, the Sassanians take control from Parthians and recover Mesopotamia from Roman Empire. On western and northern frontier the pressure from German tribes became more intense from German tribes. they were organized by clans, on family bases and were led by the king, who was related to the royal family. The assembly of the fighting men chose the king. In the third century the most aggressive Germanic tribes were Goths. They put pressure on Danube frontier and later penetrated the empire.
... throughout the empire, the education system for Roman children, and trading all over the Roman Empire, Roman rule benefited the whole empire, not just ... Rome and Italy. It is clear that all of the rules had ... hand, a few aspects of Roman rule cause controversy to the argument: Roman rule benefited the whole empire, not just Rome and Italy ...
The pressure from the Goths and Sassanian dynasty made the Roman Empire weaken its Western and Northern frontiers, that allowed the other Germanic groups, such as the Franks and Alemanni break in. The invasions of the barbarians brought many consequences. By the second century the roman army weakened and was made up of mostly romanized provincials. Roman Empire experienced great financial needs and inflations. Septimius Severus ( r 193- 211) was forced to double the pay of the solders due to inflations, this increased the imperial budget by almost 25%. To raise the money for the army the emperors were forced to make new taxes, confiscate the property of rich, debased coinage, and even sometimes selling palace furniture.
But it was still hard to recruit troops. Due to the barbaric attacks, agricultural production decreased, shortage of workers for the large farms became a great problem. Piracy and the neglect of ports and roads reduced trade. The state itself started taking on a military appearance. the great distinction between the lower class, Humiliores, and the upper class, Honestiores, became more visible. Lower classes, like peasants were tied to their land, soldiers to the army, citizens of upper class to the collection and payment of the taxes.
The upper class, however, had more privileges. They were given lighter penalties, had the right of appeal to the emperor, and could not be tortured. Although the empire did improve a little bit with time, it never got to flourish as it used to.