this is my anser to question from my friend
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I will give you some data about your question before, "Why Japan got into the WW2 with Germany".
This is big and difficult question for even most of Japanese.
Based on how they digest about this, their viewpoint and feeling and affinity to their own country and even to themselves totally differ.
As to my understanding, I write below. I think this is rather neutral and realistic viewpoint.
Then, I can explain step by step the historical progress, but it will be complex and take many words. So I indicate several main points.
BAD RELATIONSHIP BETWEEN JAPAN AND USA
1) In long term background, from about 1890s to 1945(end of war), Japan was not so in good relationship between USA. Both country had conflict in Cina(especially northeast part) interest. And Japanese immigrants to USA had bad treatment from USA legally in that term,
USA AND BRITAIN TEAM GOVERN THE WORLD AND 2ND LEVEL COUNTRY DIDN'T LILE THAT
2) In early half of 20th century, USA dramatically became powerful, their power exceeded British Empire which was the king of 19th centuries. Then, British Empire decided to cooperate with USA. And then, USA and BE teams was the almost dominator of the world and they governed the world and had better intererest from the world system. So, other strong country at that age, lile Germany and Japan did not like that situation. French power was rather declined at that time.
JAPAN-UK RELATIONSHIP CHANGE
3)Japan and UK was in good relation since 1904(Japan-UK alliance) by 1923(expilation of it). It worked good for Japan to win in Japan-Russia war.
But, because of the reason like 1) 2), their relation getting worse and USA intended this alliance break. and then, this expired and not revised. Some say that this expiration between UK and Japan was one of the most important change of the world power balance system, considering the result in the long span, and some say, if this alliance continued longer, Japan would not fail to select, which to ally, in WW2.
JAPAN-CHINA WAR AND JAPANESE POLITICAL STRUCTURE
4)Japan started to battle with China since 1931, and more apparently officially since 1937, this continued long to 1945(end of WW2).
By the way, Russia(Soviet), they utilized their big landspace to run away every time and come attack on both sides. In 1814 Napoleon war, in 1914 WW1, 1945 WW2, they did so and won every time.
China, like Russia, utilized their big land, running away in almost all battle and they come for guerrilla antivity. Japan occupied many cities. but it was point and lines between cities. all other rural land space was in china army, Japan shouold have end this war as soon as possible, but they missed some chance to end, pushed by tough elements(from government side, and from public side). And this war made other countries, which had interest in China, hostile and antagonistic to Japan. If Japan could end this war early, Japan would not get into the WW2 in bat shape. This war made relation between Japan and all other countries of League of Nations go bad, actually.
The biginner of this war at 1931 was some lower class officer. And promoter of the war was higher class office in Army, they were not correctly commanded by the government. Army department and non-Army department had same authority under the Emperor. And Emperor do nothing. He sometimes commented negative words about the war between China. But it only made the Army minister in difficult situation who need to coordinate the agressive attitude of of their juniors and Emperor's negative attitude for war. So Emperor decided not to say anything actually. He regulated himself only to acknowledge the decision of Cabinet(formed by Army minister and non-Army ministers)
So it was appear that system was not good. I think civil control is better one.
BAD JUDGEMENT ABOUT GERMANY SITUATION
5)Japan was seeing the situation of WW2, between the Axis(Germany and Itary) and the Allies(USA, British, (France was actually early defeated by Gremany) etc). Seeing the powerful attack and success of Germany, Japan decided to go with Germany. This was actually bad judgement, Japan didn't know that actually Germany is becomming in difficult situation.
MOST OF JAPANESE LEADERS THOUGHT THAT NOT TO PARTICIPATE IS RATHER BAD
6)Japanse governmet ministers and all ex-prime minister thought that if Japan didn't participate in this WW2, do nothing, Japan will decline in the competition of the world, which will make rather small effect on the world. But if participated as the side of the Axis, it would be actually hard to win,(they know that to defeat USA is almost impossible), may be lose, but possibly a chance is to lesson the effect of the USA to asia area and world, by making peace treaty in good point after half to one and half year battle. (but actually, 4 ex-prime minister and 3 Navy General including Yamamoto Isoroku insisted not to war. And emperor didn't wanted to go war actually, but he did not make political comment)
And Japan intended to liberate Asia colony from European empires and make good economic community between indipendent countries, having many meeting with leaders of these countries.(of course USA didn't say so) I don't know what if this is realized. But, for sure, it would be dependent on power balance, between relatively controlling countries and relatively controlled countries, like current world.
I hope these help you with some understanding.