> Why Japan joined WW2? Because they were playing catch up with European powers and doing what they did to Japan a some time earlier, and were trying to avoid the fate of China (see Opium wars)
That is not a very accurate take of Japanese involvement in WW2. Japan was planning several wars of naked territorial expansion during WW2, invading China twice in the 1930s, calling off an invasion of the Soviet Union after a border incident they started didn't go their way, demanding that Vichy France hand over French Indochina, and of course its very well-known invasion of US, British, and Dutch colonies to better secure needed supplies for its ongoing war with China. By WW2, Japan didn't see itself as playing "catch-up" (that period would have been the Meiji period, about 70 years prior to WW2), and instead saw itself as racially superior; nor did the European powers see Japan as an inferior power playing catch-up, but instead as a competitor and likely future adversary.
> Why Germany and Italy were heavily involved in both WW? Because they were the only European country with no colonies, in part due to their recent unification (specially Italy in this case), and the other European countries were screwing with them.
Italian Somaliland, Triplotania, Cyrenaica, Eritrea, German West Africa, German Southwest Africa, German East Africa, German New Guinea, German Samoa. (Germany was especially uninventive with its colony names). Italy was enticed into the war by promise of territory, but the promised territory was Sudtirol and the Dalmatian coast, which would be part of Italy proper and not any Italian colonies. Japan itself joined the war primarily to steal Germany's colonies in the Pacific, which they did.
That is not a very accurate take of Japanese involvement in WW2. Japan was planning several wars of naked territorial expansion during WW2, invading China twice in the 1930s, calling off an invasion of the Soviet Union after a border incident they started didn't go their way, demanding that Vichy France hand over French Indochina, and of course its very well-known invasion of US, British, and Dutch colonies to better secure needed supplies for its ongoing war with China. By WW2, Japan didn't see itself as playing "catch-up" (that period would have been the Meiji period, about 70 years prior to WW2), and instead saw itself as racially superior; nor did the European powers see Japan as an inferior power playing catch-up, but instead as a competitor and likely future adversary.
> Why Germany and Italy were heavily involved in both WW? Because they were the only European country with no colonies, in part due to their recent unification (specially Italy in this case), and the other European countries were screwing with them.
Italian Somaliland, Triplotania, Cyrenaica, Eritrea, German West Africa, German Southwest Africa, German East Africa, German New Guinea, German Samoa. (Germany was especially uninventive with its colony names). Italy was enticed into the war by promise of territory, but the promised territory was Sudtirol and the Dalmatian coast, which would be part of Italy proper and not any Italian colonies. Japan itself joined the war primarily to steal Germany's colonies in the Pacific, which they did.