Final answer:
The decline of the Roman Republic was caused by internal factors such as the influx of proletariats from displaced farmers, the concentration of wealth among elites, and a breakdown in traditional patron-client systems, as well as external pressures like threats from the Sassanids and barbarians, leading to economic and political instability.
Step-by-step explanation:
Factors Leading to the Decline of the Roman Republic
The decline of the Roman Republic was influenced by a multitude of factors, both internal and external. Significant internal disruptions began following the Punic Wars when Roman soldiers returned to find their lands taken or neglected, leading them to move to the city of Rome and join the growing proletariat class. With the majority of Roman citizens originally being small family farmers who owned property, this was a significant shift in the demographics and economy of Rome. The social system was further strained by the concentration of wealth and land in the hands of elites, leading to a breakdown in the patron-client relationships critical to the Republic's political structure.
Rome also faced severe external pressures, such as the threat from the Sassanids and well-organized barbarian groups. These pressures demanded constant military vigilance and resources, which further exacerbated the Republic’s internal problems. Economic challenges rose to the forefront as the loss of western territories led to a sharp decrease in tax revenues, thereby undermining Rome’s ability to finance its defense and maintain stability.
As a result, populist leaders like the Gracchi and military commanders like Sulla arose, reflecting the underlying societal conflict between the aristocracy and common citizens. This conflict and the transformation of Roman society illuminated the inability of the Republic's institutions to adapt, ultimately culminating in the demise of the Republic and the rise of the Roman Empire.