Historians are used to consider the Manchurian incident as the seizure of the Chinese town of Mukden in September 1931, followed by the intervention of Japanese troops into Manchuria. This historical event is often called the Mukden incident as well.
To justify the invasion into the territory of Northeast China, Japan claimed that China organized sabotage against Japan, exploding the “Liǔtiáo Bridge” near the northeastern border of Manchuria. However, these were, in fact, the Japanese officers of the Kwantung Army, who arranged the explosion of a small section of the railway on September 18.
In the Japanese press, this section was referred to as the “Liǔtiáo Bridge,” although it was aсtually a small section of the Japan-controlled South Manchurian Railway built on the plain. This propaganda was necessary to make the accusations against China more convincing. Moreover, in case of a successful operation, after blowing up a section of the railway, Japan would not have to spend money on the restoration of a real bridge but could proceed immediately to a military operation. In reality, the explosives did little damage to the railway, and the trains continued to use this route.
It is widely believed that the Japanese government was not aware of the sabotage and that it was worked out by officers of the Kwantung Army on their initiative, but this contradicts the rules of the Japanese Imperial Army. The Manchurian incident led to the international isolation of Japan, and its subsequent withdrawal from the League of Nations in March 1933. It is also seen as one of the most important milestones in anticipation of World War II.
There are several hypotheses regarding the reasons for Japanese invasion. Firstly, Japan expanded the territory of its controlled lands, so its military presence in Manchuria was necessary to protect the Japanese colonies in Korea and Taiwan. Besides, Japan needed Manchurian resources like iron, coal, oil, rubber, and lumber.
So, Japan created a puppet state on the territory of Manchuria, under the name Manchukuo, which was ruled by Pu Yi, the former emperor of China. Such a form of invasion was necessary for Japanese propaganda since Japan did not intend to acknowledge its presence in Manchuria openly. Japan allegedly supported the emperor and advocated the struggle against the nationalists and Soviets. In reality, Japan was worried about the unification of China by Chiang Kai-shek, the leader of the Chinese nationalists, and the increasing Soviet pressure on Manchuria from the north.
The sabotage and subsequent invasion became possible because the Japanese Kwantung army was deployed in Manchuria at that time. The seizure of Manchuria began with the artillery attacks on the Chinese garrison on the next day after the explosion; within three days, reinforcements from Korea arrived, and the invasion started. It lasted for three months before it was officially sanctioned by the newly elected Japanese Prime Minister in December 1931.
The Chinese army of 80,000 troops was much larger than the Japanese army of 11,000 soldiers. Nonetheless, the Japanese did not meet resistance, since half of the Chinese army was scattered throughout the vast territory of Manchuria, while the other half was stationed south of the Great Wall, thousands of kilometers away from the battleground. Besides, the Chinese troops had poor material support and morale, and the Japanese were aware of this, as many Japanese officers worked as advisers to the Chinese military commanders.
Therefore, the Chinese ruler, Chiang Kai-shek, ordered to pursue the policy of non-resistance. He withdrew the Chinese troops from Manchuria, saying that the League of Nations will determine the outcome of the case. The Lytton Commission, appointed by the League of Nations to investigate the situation, recognized Japan as an aggressor in the 1932 report. Japan withdrew from the League of Nations in March 1933, but the occupation of Manchuria continued until 1945.
The Pacific Ocean theatre of World War II unfolded around the confrontation between the regions of the Pacific Basin controlled by Japan and the areas controlled by China. League of Nations never recognized the puppet state of Manchuria.