Why did the Great Wall gradually fall into disrepair under the Qing dynasty?

Under the Qing (Manchu) dynasty (1644–1911/12), the Great Wall of China gradually fell into disrepair primarily due to a shift in imperial policy.

Rather than relying on the wall for defense, the Qing rulers adopted a strategy known as huairou ("mollification"). This approach sought to pacify the leaders and peoples of Mongolia, Tibet, and other regions by respecting their local social, cultural, and religious lives. Because this diplomatic strategy proved successful in maintaining stability along the northern frontier, the necessity for the wall as a military fortification diminished, leading to less frequent repairs and its eventual decline into ruin.1