Japan was interested in building a larger empire in Asia and the Pacific. This meant they were bumping up against the spheres of influence of the Americans, the British, and the Russians. Who, coincidentally, all happened to be opposed to the Nazis (Although the American opposition was relatively tepid at that point.)
Japanese perspective: Hey, the western powers are in the middle of a big fight! This would be a great time to snatch up some of their overseas territories!
German perspective: Hey, having someone else to harass the Allies is a great thing! It bleeds away resources that could otherwise be used against us!
In the long run if the Axis had prevailed you probably would have had a three-sided replay of the Cold War, with Nazi Europe, Imperial Japan, and Fortress America jockeying for advantage, each one trying to play the other two off each other.
Imperial Japan began it’s conquest of Asia in 1931. The Nazis were involved in the Spanish civil war 1936-1939. Imperial Japan invade China in 1937. The Nazis invaded Poland in 1939. Imperial Japan objected to G.B. and U.S. refusal to continue to trade war materials to Imperial Japan. The Nazis objected to the U.S. continuing to aid Germany’s enemies.
When Imperial Japan started it’s war with the U.S. and G.B., Hitler was more than happy to, finally, officially, go to war with the U.S… It was well known among military minds of that time that the U.S. was NOT prepared to fight a long term or extended war with a modern (for that time period), mechanized military. Too little experience, too few weapons, ships, tanks, planes, and too few soldiers and sailors. No one in 1939 expected the U.S. to do well (except for Churchill).
Neither Germany or Japan had any particular loyalty to the other. “The enemy of my enemy is my friend” is not a basis for long term friendships. Mutual distrust would be the best they could manage. Assuming the Axis had won the war, Hitler or the Imperial leadership would have objected to sharing the world with anyone else and would have found an excuse to attack the other.
But seriously, they both had similar political ideals. They both wanted territory through conquest, and at least at the time their desired claims didn’t conflict too much. It is impossible to speculate on what they’d do if they won, but it’s not quite correct to say they hated all races equally. Lebensborn was an attempt to Germanify more “pure” races. And Jews were clearly at the bottom, but black Germans had an not great but not terrible time during the war.
Early on, the Germans were training and equipping the Nationalist Chinese. They thought that the Chinese would be good allies, esp. against the Russians. But as things went on, it became clear that the Japanese would be far more useful. Although the level of cooperation never matched what they previously had with the Chinese.
The German-Japanese alliance wasn’t a tenth as awkward as the US&GB-USSR one. The West was fighting for Democracy and all that. The USSR was fighting to expand totalitarian Communism. And since the European war made Allied cooperation critical, the propaganda system could barely cope with it. German-Japanese propaganda was trivial by comparison.
No official deal was made about splitting up the world. But the general presumption was that Japan would get everything east of the Urals and down to British India, Germany (and friends) would get the rest of Europe plus whatever parts of Africa it needed. The Americas were imagined becoming something like client states-minor allies of Germany. (If anything at all.) Although I’ve seen some people who picture Japan taking everything west of the Rockies. Not sure where that comes from. The Panama Canal might have been particularly desired by Japan.
It appears that while the alliance was full of high level discussion; poor planning, little on-the-ground coordination and a general mistrust of one another doomed the partnership from the start. There might have been some early successes in spreading Commonwealth forces throughout the globe during the early years of the war, but it doesn’t appear that it was a deliberate strategy, but more of a product of coincidental expansion goals. Whatever limited opportunity that presented was lost by the time Operation Torch sandwiched the Africa Korps.
Japan/Germany would never enjoy control of the high seas, a secure trade/military route; nor did they appear to make any serious attempt at a unified command structure, share tech (aside from a few chunks exchanged via submarine), or collaborate on intelligence.
Yeah, I actually struggled a bit writing that line as I know it was a bit touch and go there for awhile in regards to Allied naval strength. It’s certainly possible that Japan could have held naval superiority for period of time, but I wonder if it would have been long enough for them (and Germany) to establish routes strong enough to provide mutual benefit in the face of Allied industrial production.