They must have had diplomatic relations. Both politically and militarily, if the old “enemy of my enemy” didn’t apply there, it never would.
Of course the inherent racism and mutual antipathy of both parties was fundamental. But so was National Socialism and Bolshevism. (And, later, Democracy and Bolshevism, of course.)
There were some exchanges. A force of Uboat called the Monsun Gruppe served in the Indian and Pacific Oceans and caused some anxiety for the Royal Navy.
The Battle of Madagascar is the only time that the European Axis and the Japanese fought alongside one another; Vichy troops opposed British landings and a Japanese submarine caused the battleship Ramallies to be badly damage, never fully repaired she was.
There were some technical support, the Germans provided the Japaness with an example of their *Amerika * Bomber. Also on nuclear research.
They were allies. (See Axis")
As such they certainly had full-scale diplomatic missions.
The German Ambassador to Japan for most of the war was a former general named Ott. He features prominently in a book I read about the famous spy Richard Sorge, who worked for the USSR. Sorge became such an intimate friend of Ott’s that Ott gave him unsupervised access to his office and to all kinds of privileged information. Sorge’s eventual arrest probably led to Ott’s getting fired. I do not know who his replacement was.
Absolutely not.
The idea is ridiculous a priori, and is unsupported by a book I read on the subject: Heisenberg’s War.
I know Hitler was impressed by Japan’s military record over the centuries and several days after Pearl Harbor he declared war on America first even though he wasn’t obligated to. Relieved FDR of not having to try to convince America fight Germany and Italy instead of making the Pacific “our war”. Sounds like hair splitting but Great Britain and France didn’t declare on the Soviet Union when they invaded Poland in September 1939, just Germany. The agreements they had with Poland said they would come to their aid if Germany attacked, a Russian attack wasn’t mentioned.
Were there any German army officers training Japanese army troops in the 20s and 30s? The German military was drastically reduced by the Treat of Versailles and a whole bunch needed work. I’ve heard of them training Chinese troops where the central government had insurrections with various warlords. But were there German advisors in Japan teaching modern techniques with machine guns, tanks, poison gas? Japan was with the Allies in World War I but felt unduly restricted by the Washington Naval Treaty of 1922. The prevalent political philosophy worldwide was countries got rich with colonies and while Japan had Korea, for them to grow there was China with a huge population, Thailand far away and a bunch of areas controlled by Great Britain, France, Netherlands and United States
The Germans attempted to send some uranium oxide to Japan on U-234, but the sub surrendered to U.S. forces before delivery.
I need to see USN eyewitness primary source documentation to believe there was any uranium on that boat.
This is a case where Wiki cites will not do.
Would have been more appropriate to send it on U-235.
Couldn’t. U-235 was sunk a month before then.
Besides that, if the shipment had been done earlier on the other sub it might have produced a critical mass of U-235! :eek: 
Don’t know why you’re so concerned about wiki when it cites its sources in in the article, but here;
From The Japanese Submarine Force and World War II
Speaking of submarines this book, War and Diplomacy Across the Pacific, 1919-1952 might be just what the OP is after, and has some telling info. Whereas the Anglo-American alliance was sharing nuclear secrets and ULTRA, in 1943 the Germans were worried about supplying Japan with new u-boat plans over concerns about patents.There was no equivalent to SHAEF, or anything remotely like it; “[Admiral] Raeder’s suggestion of January 1941 for some kind of supreme command to co-ordinate allied strategy was ignored, apart from subsequent approaches from the Japanese side in 1942 to send an Imperial delegation to Germany to provide a clearer picture of the deteriorating situation in the Pacific.”
There is also telling language in a briefing for Grand Admiral Donitz in 1943;
“In all dealings with the Japanese, their mentality must be taken into account. They are very sensitive, sly, clever and adroit at changing tactics, and can only with difficulty overcome a certain sense of suspicion towards the white race, even in their dealings with allies…The arrogance they demonstrated in the first few months…has in the meantime abated. It currently takes the form of…criticisms of our conduct of the war in Europe”
You might check out the book Hitler’s Japanese Confidant* by Carl Boyd.
*Subtitled General Ōshima Hiroshi and Magic Intelligence, 1941-1945
I read somewhere that the crewmen of the U-234 chuckled among themselves about the “mislabeling” of those crates of some very heavy unknown substance they were taking to Japan. I think that the thinking among the Germans and Japanese about coming up with atomic weapons only went as far as dirty bombs, no fission weapons.
Are you sure? I don’t think anyone realized at the time just how ‘dirty’ nuclear radioactivity was.
Even the USA, who had developed the bomb, didn’t – they sent troops onto the test site in New Mexico soon after that explosion, and then soon after Japan’s surrender, they sent officers into Hiroshima & Nagasaki to check out the results. Many of those soldiers subsequently suffered medical problems in later years.
And a dirty bomb isn’t that effective a weapon – just tossing nuclear material about, without a nuclear explosion, mostly triggers reactions that cause diseases & premature death, often years later. Not particularly effective if you’re trying to hurt the army that is going to invade yiur island in the next few days.
"Dirty’ bombs are effective now as a terror weapon against a civilian population. Because now everyone knows the danger of nuclear radiation, and will over-react and cause panic in the area. In 1945, nobody understood enough to be panicked by such news.
Was it over when the Allies invaded Poland?
Oh, nevermind.
You are suspicious because ? Because japan had no need for material to make watch hands glow in the dark ? indeed they did, and they would have made many glow in the dark watch hands from it.
Deutchland had not enriched uranium ore, and so they could only send natural uranium …
I am suspicious because:
(1) Germany would not have wanted to assist any other country, not even an ally, in obtaining nuclear weapons, and
(2) Germany needed literally every gram of uranium in its possession for its own nuclear weapon program.
As for glowing watches I have always heard that the illuminating element was radium.
Since I’ve commented at some length on the U-234 story on the boards in years past, starting from a position of some scepticism given the then available evidence, I suppose I should try to lay that whole side issue to rest.
To quote from myself in this old thread, largely based on Joseph Scalia’s recommendable book Germany’s Last Mission to Japan:
So the uranium was on board as part of Japanese requests relating to bomb research, but it’s not obvious that Berlin ever realised this.
The simple answer to the OP’s question is that they had full diplomatic relations, plus sought to help each other wherever it was in their mutual interest. Prior to Operation Barbarossa in 1941, it was fairly easy for them to pass materials between themselves. But the geographic distances then made anything largely impractical once the route through the USSR was blocked.