Question

Why did japan join in the second world war?

Answer 1

 is actually that Japan never even wanted to enter WW2 but were forced to when the US embargoed natural resources to Japan when seeing them invade the Chinese and because America would have contended the Japanese in the aggressive expansion in Southeast Asia.

Anyway, the real reason why Japan attacked China,the US and the rest of Allies is that in the 1930’s , Japan was going through a resource shortage in their country even to feed people and needed resources . And also they had gained nationalism by beating the Russians in 1904 and seizing control of German possessions of Southeastern Asia .Now, with the urge of resources and with rising nationalism and seeing the threat of US in their imperialistic ambitions. That is why Japan declared war against the US in Dec 7/8 and attacked Pearl Harbor.

(But the reasons for attacking Pearl Harbor is different. The Japanese knew that America has industrially and economically superior to them. So, if the Japanese let the American war machine time to strike then Japan will surely lose to the war. Therefore, Japanese leaders thought that they needed to destroy the as much of the existing US Pacific fleet and then capture so much of American and their allies islands and deal such a blow to the Americans that the Americans will negotiate to the Japanese on their terms. So, all of the plan should be implemented before American industries can produce new ships. Therefore, to destroy as much of the US Pacific fleet as possible, the Japanese attacked Pearl Harbor