Japan's foreign policy aims ( expansionist policy )
to control resources. as japan's economy was badly affected by the great depression they needed raw material and markets to sell their goods thus japan had her eyes on Manchuria. Manchuria can provide japan with cheap man power, raw materials and overseas market for japans good.
Japan aggression in china
In 1931, Japan conquered Manchuria but china did not put on a strong fight thus it was easy to control China.
Failure of LON
In 1931, When japan invaded Manchuria, Lon was slow in response it took a year to respond to the lytton commission. By then , japan had already occupied Manchuria. so there is no action from LON only verbal condemnation therefore japan become more bold and planned to attack China
they signed neutrality agreement with japan. so japan does not have to fight two font war, they are able to move more troops and resources from borders to more vital areas. this gave japan enough man power to plan invasion of SEA
The washington naval conference there restricted the number of warship to the ration to 5:5:3 where japan only had a ration of 3. . The neutrality acts of 1935 where US would not ship war material to countries at war made it hard for japan to obtain resources for war. therefore, japan saw these as a threat to its survival either to leave china or invade SEA for resources.