The Japanese justified their imperialism in multiple different ways, depending on what territory is in question.
For China, there was a fake attack on Japanese property, performed by the Japanese themselves, so they invaded Manchuria with the justification that their citizens were in danger.
Korea and Taiwan were justified in the sense that some countries had colonies which they used for resources and as market for their products, so the Japanese justified it in the manner that they also deserve to have such territories.
For some territories they conquered there was no real justification though, and the Japanese didn't really bothered with making excuses anymore.
"The tenets state that <span>Japan shall neither possess nor manufacture nuclear weapons, nor shall it permit their introduction into Japanese territory"
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So the Three Non Nuclear Principles were intended to keep Japan from using and making nuclear weapons.
<span>Religion served as a motive for colonization, as well as a form of government, and a reason for conflict</span>
