Why did millions of Shandong peasants migrate to Manchuria Inner Mongolia and Korea between 1923 and 1930?

Between 1923 and 1930, more than four million peasants migrated from Shandong to Manchuria, Inner Mongolia, and Korea primarily due to severe economic hardship and environmental instability.1

For centuries, agricultural practices in Shandong—specifically the clearing of land without adequate flood control—led to disastrous soil erosion and the degradation of valuable farmland. These conditions were significantly exacerbated in the 19th and 20th centuries by shifts in the course of the Huang He, which caused frequent, devastating floods. The resulting food shortages and natural calamities created an environment where subsistence became increasingly difficult, compelling millions to seek better opportunities elsewhere.1