On the night of September 18, 1931, Japanese officers used an explosion near the Japanese-controlled South Manurian Railway as a pretext for military action. Japanese forces quickly occupied Mukden (now Shenyang), turning a local “incident” into a wider invasion of Manchuria. This event is widely seen as a key step in Japan’s expanding military influence on the Asian mainland.
As fighting spread, the dispute moved to the League of Nations, reflecting China’s strategy of seeking international pressure rather than a full military response. League discussions emphasized restoring order and pulling troops back toward the railway zone. This early diplomacy highlighted the League’s limited ability to enforce decisions during fast-moving military events.
In the weeks after Mukden, Japanese forces spread control beyond Shenyang into other key areas of Manchuria. The operation went far beyond protecting a railway, creating facts on the ground before international investigations could conclude. This expansion laid the practical foundation for a new Japan-backed political order in the region.
The League of Nations appointed the Lytton Commission to investigate the causes and consequences of the Manchurian fighting. The commission traveled in the region in 1932 and gathered testimony and evidence from multiple sides. Its work aimed to provide an official international finding that could guide a settlement.
On January 7, 1932, the United States issued a note stating it would not recognize territorial changes imposed by force. This policy—later called the Stimson Doctrine—signaled that major powers could reject the legitimacy of conquest even without direct military intervention. The doctrine became an important diplomatic response to Manchuria’s changing status.
From January 28 to March 3, 1932, Japanese and Chinese forces fought in and around Shanghai. Although separate from Manchuria, the clash raised the broader stakes of the dispute and increased international alarm. It also showed that the Manchurian conflict could trigger violence in other strategic Chinese cities.
On March 1, 1932, the former Qing emperor Puyi was installed as Chief Executive of Manchukuo. Placing a former Chinese emperor at the head of the new regime was intended to give the state an appearance of legitimacy. In practice, Manchukuo operated under strong Japanese influence and military protection.
On March 9, 1932, Puyi’s inauguration was held in Changchun (later renamed Xinjing). Contemporary diplomatic reporting described the ceremony as being directed by Japanese authorities, reinforcing the view that Manchukuo was not fully independent. The inauguration marked the transition from military occupation to a formal Japan-backed government structure.
On September 15, 1932, Japan signed the Japan–Manchukuo Protocol, confirming Japan’s recognition of Manchukuo. The agreement also enabled the continued stationing of Japanese forces, strengthening Japan’s control over security and politics. This step deepened the international dispute by treating the new regime as a state partner.
In October 1932, the Lytton Commission’s report concluded that Japan’s actions could not be justified as self-defense and that Manchukuo did not represent genuine independence under the circumstances. The report recognized Chinese sovereignty claims while recommending steps toward a negotiated settlement. Japan rejected the findings, worsening the diplomatic break with the League.
On February 24, 1933, the League of Nations Assembly adopted conclusions blaming Japan for events in Manchuria. Japan’s delegation dramatically withdrew from the meeting after the vote, signaling that it would not accept the League’s judgment. This moment became a symbol of the League’s weakening authority over major powers.
In the aftermath of the Manchuria dispute and the League’s vote, Japan moved to leave the League of Nations rather than accept its recommendations. The decision reflected Japan’s preference for regional control over international oversight. The withdrawal also reduced the chances that collective diplomacy could reverse Japan’s position in Manchuria.
On May 31, 1933, Chinese and Japanese military authorities signed the Tanggu Truce (Tangku Truce). The agreement created a demilitarized arrangement south of the Great Wall and effectively reduced the immediate risk of large-scale fighting in North China. It also reflected that Japan’s gains in Manchuria had become difficult to reverse through diplomacy alone.
Manchurian (Mukden) Incident and creation of Manchukuo (1931-1932)
