Inner Manchuria came under strong Russian influence in the 1890s with the building of the Chinese Eastern Railway. Japanese influence replaced Russian in Inner Manchuria as a result of the Russo-Japanese War (1904 - 1905).

Between World War I and World War II Manchuria became a political and military battleground. Japanese influence extended into Outer Manchuria in the wake of the Russian Revolution of 1917, but Outer Manchuria had reverted to Soviet Russian control by 1925. Japan took advantage of the disorder following the Russian Revolution to occupy Outer Manchuria but Soviet successes and American economic pressure forced Japanese withdrawal.

After the Japanese invasion of China in 1931, Japan declared the area independent from China on February 18, 1932 as the Great Manchu State (Manchukuo). The city of Changchun, renamed Xinjing, became the capital of the new entity.

The Japanese installed Puyi, who as Hsuan Tung had been the last emperor of China, as chief executive in 1932, and in 1934 he became emperor of Manchukuo with the reign name of "Kang Teh". Manchukuo thus became the "Great Manchu Empire". In this manner Japan formally detached Manchukuo from China in the course of the 1930s. With Japanese investment and rich natural resources, the area became an industrial powerhouse. Eventually, Japanese became the official language taught in Manchukuo schools and Shinto became the national religion.

Few nations recognized the new state, and the League of Nations declared that Manchuria remained rightfully part of China, leading Japan to resign from the League in 1934. Of the major powers only Japan, Italy, and Germany recognized Manchukuo diplomatically. In addition Manchukuo gained recognition from the Japanese collaborationist government of China under Wang Jingwei, El Salvador, Costa Rica and the Vatican City State.

Prior to World War II, the Japanese colonized Manchukuo and used it as a base from which to invade China. The Emperor had no power at all, and all of the Manchu ministers only served as front-men for their Japanese vice-ministers, who actually made all decisions.

On August 8, 1945 the Soviet Union declared war on Japan in accordance with the agreement at the Yalta Conference, and invaded Manchukuo from Russian Manchuria.

Some Manchukuo stamps:

 

 

During the civil war, nationalist forces fighting communists held the southern portion of Manchukuo until November 1948, and during 1946-48 issued stamps for this area (North-Eastern Provinces):