Tanggu Truce
The Empire of Japan had been pursuing its expansionist ambitions in China since the late 19th century, and the situation began escalating in the early 1930s. In September 1931, the Mukden Incident resulted in the Japanese Kwantung Army completely occupying the three northeastern provinces of China and defeating the forces of the pro-Nationalist warlord who had ruled the region, the "Young Marshal" Zhang Xueliang. The Kwantung Army later took part in establishing the Japanese puppet state of Manchukuo in 1932 under the rule of the last Qing emperor, Puyi. Shortly after that the three eastern Mongolian leagues–ancient regions of Inner Mongolia–were occupied and annexed into fledgling state of Manchukuo. The hostilities in the Manchuria region between the Republic of China and Japan ended in May 1933 with the signing of the Tanggu Truce. However, due to the lingering Japanese territorial ambitions and Chinese public opinion being against the harsh terms of the agreement, it was only a temporary respite.