The Great Wall of China was primarily built to protect China from invasions coming from the north, especially from Mongol and other nomadic steppe groups located in what is now Mongolia.

Core idea

  • The main defensive purpose of the Great Wall was to block or slow attacks by northern nomadic peoples, particularly the Huns (Xiongnu) and later the Mongols and related tribes, whose homelands were in and around present‑day Mongolia.
  • In modern terms, this means the wall would best protect China from an invasion by its neighbor Mongolia , rather than from southern or eastern neighbors like India or Korea.

Historical background

  • Early unified sections of the wall under the Qin dynasty were extended specifically to defend against the Xiongnu (often compared to an earlier Mongol-type power) on the northern steppe.
  • Later dynasties, including the Ming, strengthened and rebuilt long stretches of the wall to resist repeated incursions from Mongol, Tatar, Oirat, and Jurchen groups north of China’s agricultural heartlands.

Why the northern neighbor

  • The geography of the wall runs mainly east–west across northern China, marking a boundary between settled farming regions to the south and nomadic grazing lands to the north, making it strategically suited against northern invaders.
  • Nomadic cavalry armies from the northern steppes were the consistent long-term military threat, so fortifications, watchtowers, and signal systems along the wall were oriented toward that direction.

Answer in textbook style:
The Great Wall would best protect China from an invasion by Mongolia (northern nomadic peoples based in that region).

Information gathered from public forums or data available on the internet and portrayed here.