Japan From January until May 1933:[2] 2,400 casualties Taishō period Shōwa period The defense of the Great Wall (simplified Chinese: 长城抗战; traditional Chinese: 長城抗戰; pinyin: Chángchéng Kàngzhàn) (January 1 – May 31, 1933) was a campaign between the armies of Republic of China and Empire of Japan, which took place before the Second Sino-Japanese War officially commenced in 1937 and after the Japanese invasion of Manchuria in 1931.

During this campaign, Japan successfully captured the Inner Mongolian province of Rehe from the Chinese warlord Zhang Xueliang, and incorporated it into the newly created state of Manchukuo, whose southern frontier was thus extended to the Great Wall of China.

When the Chinese garrison refused, the Japanese 8th Division issued an ultimatum, and then attacked the pass with the support of 4 armored trains and 10 tanks.

Declaring the province to be historically a portion of Manchuria, the Japanese Army initially hoped to secure it through the defection of General Tang Yulin to the Manchukuo cause.

On March 12, Zhang Xueliang resigned his post to He Yingqin who, as the new leader of the Northeastern Army, was assigned the duty of securing defensive positions along the Great Wall.

Beaten back by overwhelming Japanese firepower, on May 20, the Chinese army retreated from their remaining positions on the Great Wall.

The resulting Tanggu Truce created a demilitarized zone extending one hundred kilometers south of the Great Wall, which the Chinese army was prohibited from entering, thus greatly reducing the territorial security of China proper, whereas the Japanese were permitted to use reconnaissance aircraft or ground units to make sure that the Chinese complied.