How did the Military Strategy of the great wall evolve in history

In the early days, during the Warring States period, the Great Wall was fragmented, with each state building its own sections mainly for border protection against neighboring states. The focus was on local defense, using simple earthen walls and watchtowers. As the Qin Dynasty unified the country, the strategy shifted to connecting and strengthening these walls to create a unified defense line against northern nomadic tribes. The Han Dynasty further extended and fortified it, with a greater emphasis on cavalry defense and long-range patrols. In the Ming Dynasty, which faced persistent threats from the north, the military strategy became more elaborate. The wall was built with advanced fortifications, including complex gate defenses, hidden passages, and advanced signaling systems. The use of firearms also influenced the design, with embrasures for guns. Over time, the Great Wall's military strategy evolved in response to changing enemies, technologies, and political landscapes, always aiming to safeguard the empire from external threats.