The Han, Roman and Gupta empires all fell do to invasion. A strong, loyal army is necessary to protect the empire from invasion. All of these empires were first weakened by a succession weak governments. The trust and faith in the government was eroded over time. Internal strife by the people because of declining abilities of the government to govern weaken the state. The government should try to prevent internal rebellions by maintaining good governance over the people.
It caused them to be slaves
The wealthiest citizens of ancient Rome were "patricians"--meaning literally "fathers". These people were not only the wealthiest but had by far the most political sway of any other social group.
