Over time, many Han Chinese settled in Rehe anyway. In the early Republic of China, the area was organized as the Rehe Special Autonomous Mongol Territory in 1914. It was declared the Province of Jehol of the Republic of China in 1923.
Jehol was seized by the Imperial Japanese Army to form a buffer zone between China proper and Japanese-controlled Manchukuo in Operation Nekka beginning on January 21, 1933. It was subsequently annexed to the Empire of Manchukuo, forming the anto (province) of Rehe.
The seizure of Jehol was one of the most important of many incidents in the 1930s that poisoned relations between Japan and China, leading to the Second Sino-Japanese War.
After the annexation of Manchukuo by the Republic of China after the end of World War II, the Kuomintang continued to recognize the area as a separate province, reverting its name to Jehol Province, with the capital in Hailar. However, under the administration of the People's Republic of China, in 1955, the area was divided between Hebei province, Liaoning Province and the Inner Mongolia Autonomous Region.