How was the Great Wall organized into Nine Border Garrisons during the Ming dynasty?

During the Ming dynasty, the Great Wall was organized into nine distinct defense areas, or zones, collectively known as the Nine Border Garrisons.1

This military administration was structured hierarchically, with each major stronghold linked to a network of commands. A post chief, known as a zongbingguan, was assigned to oversee each of these nine zones. This system allowed for coordinated defense along the fortification, which was essential for protecting the capital, Beijing, and preventing invasions.12

The garrisons were part of a broader military establishment where soldiers were organized into units called guards and battalions. These troops were often stationed along the frontiers and strategic locations, alternating between military duties and agricultural labor to remain self-supporting.3