EDIT: I don't think it's a duplicate of this. That question asks why attack USSR while still fighting Britain (and I think the OP has a misunderstanding there because the Battle of Britain was already over and Britain did not mount much offensive power for a while after that). Also, my question is about Germany attacking USSR and Japan attacking USA. I'm asking what seems to have obligated them to this, such as prior agreements.

From a related question, I started wondering (again) why Germany ever invaded the USSR. At the time, the Molotov–Ribbentrop Pact was in effect wherein Germany was greatly supplied by Soviet material. Why would you cut off this supply AND open up the huge eastern front?

That said, let's say the Battle of Britain ended the same way and Germany has no way to invade Britain. Can't the Germans just take some breathing time and consolidate their power in West and Central Europe? Instead, something seemed to obligate them to attack USSR immediately. I cannot figure out what this "something" is.

Taking this further, if the Japanese did not bomb Pearl Harbor, then America would not have gotten involved any time soon. They seem to have felt compelled to attack America. I know they were trying to destroy the US Navy, but honestly, if you can't touch the North American mainland, they must surely have known the Americans would rebuild. So I don't see what really compelled them to attack.

It sounds to me in this situation, without attacking USSR or USA, the German and Japanese Empires would have been very stable for at least...5 years or more. There would be action between Britain and European continent, but nothing decisive. It would be stalemate there, maybe with an official truce, but stalemate at the least.

(I know about the A-Bomb too, and even if we assume America is still the only one working on it and would have it in 1945...they can't use it without air superiority. We could I guess wait until 1955 or 1960 for an ICBM, but what would Germany/Japan have by then too?)

To sum up, what really compelled Germany to attack USSR and what really compelled Japan to attack USA? Were they really obligated under some treaty or internal agreement somewhere?

I don't know if ideology can explain it. If your ideology says you have to conquer the world, then why not do it in an actual realistic way like the one I mentioned? Instead, it's as if they had some unspoken short-term deadline for all of this.

EDIT 2: Let me try to clarify a bit more: To me, it seems like there was some internal agreement saying, Hey i'll take USSR if you take USA! Otherwise I can't understand why, at the very least, both Germany and Japan didn't cooperatively attack USSR from two different fronts. They could each concentrate on one front, whereas USSR would hafta deal with two.

  • your last assertion is already wrong. There was a significant Japanese force on the Manchurian/Soviet border, and there were border skirmishes. The main reason they didn't strike north (yet!) was that they were too busy suppressing the Chinese (both the communists under Mao and the Kuo Ming Tang under Chiang Kai Chek).
    – jwenting
    Commented Jul 31, 2015 at 5:57
  • Hitler was a madman; he required no reason for his actions beyond whim. Attempting to rationalize his actions only gives them some form of legitimacy that they don't actually deserve. Commented Aug 1, 2015 at 1:10

1 Answer 1


As you asked, They did not have a treaty that "made" them attack their targets at specific times (they did have treaties of mutual protection though).

But to answer why they did, Germany at that time figured that they had Britain bottled up and blockaded so it could do no harm to them, and they already controlled all of mainland Europe. They attacked the USSR because they knew if the US, Britain and the USSR all started fighting them, they would lose (which they rightly feared seeing the outcome of WWI); So they saw the Russians as the weakest link in the group. Britain was protected by being an island, the US was too far away, but the USSR was poorly equiped, corrupt, and was slow to mobilize. They only lost to the USSR because of the climate and that when the USSR actually mobilized they pushed the Germans back and ended the German blitzkrieg they had been running since 1939.

The Japanese attacked Pearl Harbor for almost the same reasons. They, like the Germans, were out of options. They had been trying to get a treaty with the US for two years, but it always fell through. They weren't surrounded like the Germans, but they didn't have their own oil supplies. So they decided to attack the US fleet in the Pacific and hoped to ruin it, so that they could take over US islands in the Pacific and gain oil and other resources it needed.

Japan prepared for war. On 20 November it presented an interim proposal as its final offer. It called for the end of American aid to China and the supply of oil and other resources to Japan. In exchange they promised not to launch any attacks in Southeast Asia and to withdraw their forces from their threatening positions in southern Indochina. The American counter-proposal of 26 November required that Japan evacuate all of China without conditions and conclude non-aggression pacts with all Pacific powers. That meant Japan was essentially forced to choose between abandoning its ambitions in China, or seizing the natural resources it needed in the Dutch East Indies by force; the Japanese military did not consider the former an option, and many officers considered the oil embargo an unspoken declaration of war.

To Sum it up: Germany thought the USSR would be a push over for them, just like it was in WWI. Japan thought the US would back down and not continue the scene they were causing even before Pearl Harbor.

EDIT: The reason Japan didn't help Germany attack the USSR was because Japan already fought them in the decades leading up to WWII, and had a peace agreement with them. But it sounds like there is a misconception: Germany and Japan weren't allies because they were friends with each other and decided they would mutually defend each other, they were really just allies because they had similar goals and good politics in their respective countries to have an ally in Europe and Asia. They really didn't have much internal agreement at all with each other. You seem to think they had the relationship of Italy and Germany in WWII where they were coordinating efforts, Japan was really an outsider in the Axis powers, just like the USSR in the allied powers

  • That's odd, I thought Japan had about half of Sakhalin Island at this time, and there is a lot of oil there according to today's reports (maybe they didn't know that in 1941?). It seems a lot wiser if they both attack USSR (Germany from West, Japan from east). As it is, it seems like there was some internal agreement saying, hey i'll take USSR if you take USA.
    – DrZ214
    Commented Jul 24, 2015 at 1:06
  • I think that with Germany, there were also some ideological considerations. Hitler saw communism as an enemy, as did many in Britain and the US, so might have hoped that by attacking the USSR, he would gain at least neutrality, perhaps tacit support, for his conquest. But in fact the US provided material support to the USSR....
    – jamesqf
    Commented Jul 24, 2015 at 1:10
  • 1
    @DrZ214 Oil wasn't the only resource that Japan had problems gaining. the US and Britain also embargoed steel, rubber, tin, and other items needed to actually make war. it wasn't that Japan didn't have any of those resources, it is more that they couldn't get enough production out of what they already had to fit their needs.
    – Alexandre
    Commented Jul 24, 2015 at 1:19
  • 1
    I don't know why this was downvoted, it seems broadly accurate or at least as good an explanation as any on this speculative topic. That said, Japan attacked Pearl Harbour to prevent the American Navy from interfering with them taking South East Asia, i.e. Dutch and British Islands, rather than US one (which weren't many). Ideological motivations for Russia also warrants mentioning.
    – Semaphore
    Commented Jul 24, 2015 at 7:24
  • 1
    I guess you guys overlooked the Battles of Khalkhin Gol? The Japanese did attack the USSR, they were completely destroyed. Commented Aug 21, 2015 at 1:21

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