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How did the number of Han commanderies change during the Western Han period?

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Map showing the Han Empire's territory around 100 BCE, shaded in orange, covering much of eastern China and extending westward. The map also marks the boundary of modern China and highlights the Great Wall running along the northern frontier, built for protection against the Huns. Major rivers and the capital, Chang'an (Xi'an), are labeled. — Han dynasty Map showing the extent of the Han empire c. 100 bce.

During the Western Han (Xi Han) period, the number of commanderies increased significantly as the central government expanded its administrative control. At the beginning of the dynasty during the reign of Gaozu, there were 16 commanderies. By the end of the Western Han period, this number had grown to 83 commanderies, alongside 20 kingdoms.12

This growth was driven by several factors:
* Consolidation of Power: The imperial government systematically reduced the strength of kingdoms held by the emperor's kinsmen, incorporating much of their land into commanderies under central administration.12
* Administrative Expansion: Commanderies were established by dividing existing units into smaller ones or by setting up government organs in regions newly penetrated by Chinese officials.12
* Territorial Growth: Military campaigns, particularly those beginning around 135 BCE, led to the founding of 18 additional commanderies in outlying areas, such as the northeast, south, and southwest.3