The League of Nations' reaction to the Manchurian incident set a dangerous precedent by showing that aggression could be successful if met with appeasement rather than decisive action.
When Japan invaded Manchuria in 1931, the League of Nations condemned the action but failed to take any meaningful action to stop it. Instead, the League of Nations sent a commission to investigate the incident, which ultimately failed to resolve the conflict.
This lack of action and appeasement of Japan's aggression sent a message to other nations that the League of Nations was not willing or able to take decisive action to stop aggression. This encouraged other aggressor nations, such as Germany, to pursue their own expansionist policies in Europe in the years leading up to World War II.
The failure of the League of Nations to stop Japan's aggression in Manchuria set a dangerous precedent that showed aggressor nations that they could pursue their objectives without fear of consequences. This ultimately contributed to the outbreak of World War II and the failure of international efforts to prevent another devastating conflict.