Japan had a large army and navy. Since 1905, it had controlled the territory of the South Manchurian Railway
In September1931, Japan used a disturbance as an excuse to capture the town of Mukden and send troops to take over the rest of Manchuria
The Japanese pretended to give Manchuria independence. They put a weak leader in charge so they could control him
The LoN sent Lord Lytton to assess the situation. He produced a report, which said the Japanese had been wrong, but the League didn't do anything else - it failed to stop Japan and end the crisis
Japan refused to accept Lord Lytton's report and withdrew from the League in 1933
In 1933, the Japanese invaded China's Jehol Province, which bordered Manchuria
Japan signed a treaty with Nazi Germany in 1936, and in 1937 started to invade China - again the League did nothing to stop it
Japan was an important trading partner for many countries in the League. This made them reluctant to either put sanctions on Japan, or stop selling them weapons. This suggested that countries wouldn't support the League if it was against their own interests
Countries like France and Britain were also reluctant to commit money and troops to stopping Japan because they were preoccupied with dictators like Hitler closer to home
However, the League's failure to act just showed dictators like Hitler the obvious weakness of the league