Battles & Wars › Between the wars › Second Sino-Japanese War
Mukden Incident and invasion of Manchuria
September 18, 1931· Event· Asia & Pacific
Well documentedSolid records, physical evidence or scientific consensus.
Japanese officers blew up a stretch of their own railway near Mukden, blamed China, and used it as a pretext to seize Manchuria.
See it on the Battles & Wars map →What happened
On September 18, 1931, officers of Japan's Kwantung Army, which guarded the Japanese-owned South Manchuria Railway, set off a small explosion on the track near Mukden (now Shenyang). They blamed Chinese troops and, without Tokyo's approval, attacked. Within months they held all of Manchuria. In 1932 Japan set up the puppet state of Manchukuo under Puyi, the last Qing emperor. The League of Nations' Lytton Report condemned the action, and Japan quit the League in 1933.
Why it matters
It showed Japan's army could act on its own and get away with it, set Japan on a path of expansion in China, and exposed the League's weakness.
How we know
The League's Lytton Commission report of 1932, Japanese army records, and testimony at the Tokyo war-crimes trial after 1945 confirming the plot.
Still debated
How much senior army leaders and the government in Tokyo knew beforehand is still debated.
Connections (2)
▸Mukden Incident and invasion of Manchuria led to Second Sino-Japanese WarWell documented
The connection
Seizing Manchuria gave Japan a base, resources and a model of army-led expansion. In the early 1930s it pushed into Rehe and northern China, creating buffer zones near Beijing. Chinese anger grew, and Chiang Kai-shek finally agreed to unite with the Communists against Japan. When troops clashed at the Marco Polo Bridge in 1937, neither side backed down.
When and how
Northeast and north China, 1931–1937, from Mukden to the Marco Polo Bridge near Beijing on July 7, 1937.
How we know
The chain of incidents and truces between 1931 and 1937 is well documented; China officially counts a 'Fourteen-Year War' from 1931.
Debates and open questions
Whether 1937 was the inevitable outcome of 1931, or an escalation neither government planned, is debated.
▸Mukden Incident and invasion of Manchuria exposed the weakness of the order built by Treaty of VersaillesMostly agreed
The connection
The Treaty of Versailles created the League of Nations to stop aggression by collective action. When Japan seized Manchuria, the League sent the Lytton Commission, which condemned Japan but brought no sanctions. Japan simply left the League in 1933. The lesson that aggression went unpunished was noted in Rome and Berlin.
When and how
Manchuria, Geneva and Tokyo, 1931–1933; the League Assembly adopted the Lytton Report in February 1933, and Japan's delegation walked out.
How sure are we?
League records, the Lytton Report and Japan's withdrawal are documented; the link to later aggression by Italy and Germany is historians' interpretation.
Debates and open questions
Whether any League action could have stopped Japan without the US and the Soviet Union, neither then a member, is debated.