Final answer:
The existence of a “luxurious” city creates the need for a strong military defense due to the wealth within the city making it a target for potential aggressors. This has been a consistent pattern throughout history, necessitating the establishment and maintenance of armies to protect and maintain the city's wealth and power.
Step-by-step explanation:
A “luxurious” city, due to its accumulation of wealth and resources, can inadvertently become a target for attacks, thus creating the need for a strong military defense. Conflicts often arise when cities or nations accumulate wealth, as seen throughout history from the early Mesopotamian cities to the wealth of European monarchies enabling them to hire mercenaries for protection. Sociologists like Ludwig Gumplowicz and historical instances, such as warfare during the Warring States period in China, suggest that the creation of wealth often leads to power struggles and necessitates military strength for both offensive and defensive purposes.
As such, this accumulation of city wealth leads to the need for defense mechanisms against potential aggressors, driving the establishment and maintenance of armies. This dynamic has been observed across different eras, including during periods of mercantilism and the Roman Empire, where the needs of the military often had significant societal impacts, such as taxation, economic restructuring, and continuous conflict. Therefore, the need created by the existence of a “luxurious”, wealthy city is primarily the need for defense and military organization to protect its wealth and maintain its status.