During WWI Japan seized multiple Islands to the South which were controlled by Germany this was because they needed land and the resources that came with it. So the US let this happen. But The emperor got greedy and wanted more and more land(a reason for WWII). So when a country marches into another countries land what happens? Usually a war because that land was rightfully theirs. Basically what I'm trying to say is that Japan had some good reasons for fearing the US one of which was sanctions because Japan's industry would have(and was) been crippled if the US stopped giving them resources to make steel for example or have an auto industry (Mitsubishi)
