Japan invaded Manchuria because it was rich in raw materials and because Japan had no raw materials of its own, it relied on trade and because of the Great Depression there was less trading and people in Japan were literally starving.
There was an explosion on the railway and the Japanese said the Chinese had staged it and then fired at Japanese soldiers. The Chinese government appealed to the league. Instead of using military or economic sanctions, the league sent a commission to investigate Japanese aggression. They concluded that Japan had acted unreasonably and the league demanded the Japanese to withdraw, but it was too late. Japan ignored the league and just left in 1933, and continued their invasion of Manchuria.
In 1937, Japan invaded china itself.
FAILURE - the league had been humiliated. Britain and France were too preoccupied with the effects of the Great Depression in their own countries so the league was powerless.
Hitler realised that the West would not stand up to determined military action.