Why did Japan attack the USA?

Lord Fairfax

Ad Honorem
Jan 2015
Space Bat Lair
Japan invaded Indochina specifically because of their war against China, and the US involvement in China's resistance against Japanese invasion played a major role in the Japanese decision to invade the French possessions in Indochina.

The path that lead to the war between USA and Japan didn't begun with the US embargo in the aftermath of the Japanese invasion of Indochina, it actually begun earlier when the US as early as 1938 begun to adopt trade restrictions with Japan because of the war against China.
However, as Japanese records show, they wouldn't have gone to war if they could obtain oil & metals from the British & Dutch. Had FDR not brought the European allies on board with the embargo, the Japanese could have survived without US oil
Sep 2019
But did the Philippines really have any absolutely necessary supplies that could not be gained from Malaysia and Indonesia?
The US demands were two :

- immediately withdraw from French Indochina,
- give serious warranty about ending the war in China.

Nothing about Mandchouria, Korea or Taiwan.

The policy of Japon was to implement the Greater East Asia Coprosperity sphere. That entailed to oust western nations from Asia and Pacific.


Ad Honorem
Oct 2009
San Diego
Japan Attacked the Philippines because they are in Asia- populated by Asians.
WWI and II were wars fought over Germany and Japan's attempts to build their OWN empires to compete with the British, French and , increasingly, American colonial empires.
Britain and France acted to deny Germany that kind of power in WWI.

By the time of WWII Japan saw itself as the Germany of Asia- Superior, technological, and destined to rule over all of asia. They felt that Europeans had no business in Indonesia, China and the Philippines... and determined that Asia should be an Empire of Asians and. of course, among asians, only the Japanese had the superior culture and technology to rule.

So, their objective was to get the british, Dutch, French and Americans OUT of asia.
To be honest, they had good timing... The European powers were embroiled in war- and America was acting like it wanted NOTHING to do with foreign wars, Although, being a nation of largely european immigrants, America WAS devoted to helping support the European powers...
From the Japanese perspective, It looked like France and Holland were out of the picture...and the British stretched far too thin defending itself to spend much attention on asia. It looked like America was still isolationist, and unwilling to go to war.
And the Japanese Knew that americans had no particular sense of affinity for Asians and were pretty much in Asia as an afterthought, and not highly invested in it.

With Russia dragged into the war the the US now supplying most of Russia's and Britain's needs to defend themselves... Japanese leaders who had never BEEN to the US assumed that the US was a nation that would not be willing to do without its own comforts, and that its surplus productivity was stretched to the breaking point thru lend lease aid to the Allies.

To the Japanese, Hawaii was an American colony- they felt the Americans did not necessarily think of it as part of the US. And they felt that, given the situation around the globe, and the people of the US having vested interest in European support- that there would be no better time to just TAKE all US and British possessions in Asia. All they needed to do was make it impossible for the US to DO anything about it, for 4 to 6 months... and they figured the US, by that time, would be faced with having to CHOOSE- to defend Europe from Hitler... or to take back a bunch of Asian islands that the US had little real investment in. Their economic assessment was that the US, at that time, did not have the productive capacity to supply TWO wars- both of which were thousands of miles away.

As a result- they determined that their best plan was to launch simultaneous military attacks on ALL US Asian possessions... take wake and Guam to cripple US Air access to Asia... and to sink the pacific fleet to cripple the US' ability to respond with a naval action.

They were counting on the idea that Germany at the time seemed unstoppable and would overrun Russia- and then turn its attention to invading Britain.

To be fair- there was never a better time for them to take their shot at owning it all.
French and British Americans would feel some reason to send their sons to fight for their relatives in the 'old country'- but would they feel like sacrificing their sons to liberate Asians?

To that end, they woefully misjudged the psychological effect of attacking pearl harbor without a declaration of war.
Perhaps the Asian social tendency to ancestor worship caused them to imagine that US support for Britain was the primarily motivated by ancestry... rather than economics or pure political interests.

They certainly failed to understand that the US industrial capacity was potentially unlimited, and easily capable of quintupling production without any shortages of raw materials.

I often wonder what would the US response have been if the Japanese had NOT attacked Pearl?
If they had taken Wake and Guam, and the Philippines- but left the US fleet alone and not attacked pearl.... would the US populace have seen That as the last straw to get them on a war footing?

Especially if the Japanese had just surrounded the islands and the US forces and demanded they ship out and go home... rather than the whole bloody conflict and Bataan death march and other excesses of war.
Imagine the Japanese navy just blockading every US possession and demanding that US occupiers leave.

Would the US have fought that and committed itself to war in the pacific? Or just said, who cares about Asia?


Ad Honorem
Mar 2013
Japan was not some monolithic entity even just prior to the start of WWII though the militarists had been ascendant for the past two decades. There were several competing factions with the Emperor expected to provide the final approval for large changes of strategy but which proposals were submitted for that approval was the subject of intense in fighting between factions.

With the Meji ministers in charge, Japan modelled itself on the western industrialized nations and instituted huge social and economic changes- this re-organization provided Japan with the economic power and the social moral superiority to undertake to copy some Western powers colonization efforts. Taiwan and Korea were relatively already in the Japanese sphere with only China and Russia having much objection but with the Russian occupation of Manchuria, American occupation of Philippines, and the British invasion of within a year of each other around 1903 it appeared the areas for Japan to colonize were quickly getting very small.

The western powers did not want to make rules barring countries from claiming what was previously considered in the Chinese sphere since they were still eager to expand there themselves and it was Russian desire for warm water port on the Pacific, British desire NOT to have another naval competitor in the Pacific, and German desire to see Russia provoke Britain and support German interests in Asia with the occupation of Manchuria where Japan was seen as a minor power as most western states did not understand the profound transformation Japan had gone through that led to the initial British and American support of Japanese expansionist policies in Asia.

Japan did not actually seek war with Russia but their interests collided where Japan had staked its strategy around expansion in Korea while Russia had Imperialistic ambitions and already agreed to withdraw from Manchuria- Russia was not about to bow before an even smaller Asian power named Japan. The Japanese victory over Russia was shocking to pretty much everyone- Japan included. Western powers were suddenly confronted with the idea that Japan was potentially a real adversary, Russia was humiliated and its naval ambitions greatly curtailed, Britain wasn't pleased to have had a Russian naval competitor in the Pacific replaced by an even stronger Japanese competitor, Germany was disappointed to lose Russia as a potential friend in Asia, America was relieved to deal with Japan (which was viewed as more likely to side with American interests over European powers as they were both relative newcomers in the colonization game in Asia).

Japan had faced down Russia from active expansion in Manchuria which resulted in Japanese military faction hugely emboldened and with large amount of social cachet due to its defeat of a Western power and where previously military ambitions were constrained to economic policy now the economic policies came to be dedicated to supporting military expansionism. WWI weakened the European powers hugely and Japan used that time to consolidate Korea, and take over several former German islands while the Russian civil war also led to Japan occupying a very large area and participating on the side of the victorious allies giving it some diplomatic capital to use in consolidating the territorial gains Japan had made so far.

With Russia convulsed in the aftermath of a bitter civil war, China fighting its own Communists and the Great Depression distracting most of the world- Japan finally had the chance to try and grab Manchuria which was the end result of most of its manoeuvring in the prior two decades. The main problem was that with Japanese policy following military expansionism the possible trade and diplomatic moves that would have guaranteed economic success were instead aimed at providing resources for the Japanese military- the most important of which was no longer coal but oil which Japan had absolutely no access to or good relations with the current main suppliers of oil other than the U.S. and those good relations had greatly declined as Japan moved aggressively to not only occupy territory but to attempt to exclude Western commercial interests from its own sphere which was growing to encompass China. The rest of the world might be distracted but the U.S. business interests that had the ear of Washington D.C. had grand dreams for China which Japan was threatening to shatter. It should also be mentioned that Japan gained a huge reward for siding with and supplying war time needs of the WW1 allies and on the other hand lost almost its entire investment in Russia as the communists won and Russia defaulted on millions worth of loans Japan had made.

To many in Japan, the relative success that aggression had brought was the confirmation of Japan's place atop the rest of Asia and the notion of Asia for Asians and that it was the only the criminal opportunism and greed of Western powers blocking Japan from leading a new order in Asia to world domination. This idea was widely spread by the propaganda of the Imperial Japanese government and the Japanese business community. This was a misreading of the situation by the Japanese pro-war faction but led to the complete abandonment of any focus on peaceful economic opportunities by most of the Japanese business community which perceived more money could be made in Imperial adventures than open competition (not that different from the reaction of business in Germany to the rise of the Nazis).

With the U.S. stuck in the Great Depression and the commercial angst of the U.S. focused inwards, along with the new Japanese assumption of racial superiority, complete seizure of Manchuria and other Chinese territories was deemed fair game. China despite being hobbled by civil wars, poor leadership, and low infrastructure was still many times the size of Japan and had gained important loyalty from the Americans and British who saw China as their best chance of cheap opposition to Japan while neither of those nations could afford to confront Japan directly through the 1930s.

The expansion and military operations of the Japanese war in China and the occupation of Indo-China by Japan brought two factors to head- Japan realized it absolutely had to gain control of oil for itself or face a continual military liability and threat to its Imperial Empire, while the failure of appeasement in Europe had left the U.S. and European powers without any patience for continued aggression by Japan even if military confrontation wasn't desired the weakness of Japan in its lack of access to resources was viewed as the easiest manoeuvre to make and thus the sanctions and the Japanese decision to seize the resources it felt it deserved while the rest of the world was distracted with another World War.

The Japanese military had lost sight of the true strategic situation with its arrogance and even those planners and people who had doubts were easily overruled. It was also true that while the capabilities of a modern war could be deduced from current economic production and technology- there had not yet been a projection of power on anywhere close to the scale that WWII would bring and it was difficult to accept that the U.S. would care enough about Asia to build 150 new warships including over 25 carriers just for the Pacific war (not including the Atlantic) and devote more than 1/3 of its GDP toward war. Japan started WWII with 1/4 the known industrial capacity of the U.S. and ended at 1/10th effectively shrinking by about 40% while the U.S. grew by 50%.
Last edited:
  • Like
Reactions: Richardrli


Ad Honorem
Jun 2014
Lisbon, Portugal
The US demands were two :

- immediately withdraw from French Indochina,
- give serious warranty about ending the war in China.

Nothing about Mandchouria, Korea or Taiwan.

The policy of Japon was to implement the Greater East Asia Coprosperity sphere. That entailed to oust western nations from Asia and Pacific.
The policy of Japan at the time was specifically to control China. The Greater East Asia Co-prosperity sphere was an organization that was only thought out and seriously conceived by Japanese decision-makers in 1940 or so, after the Second World War was unleashed.

Before that, the overall geopolitical vision of the Empire of Japan was of the New Order in East Asia (東亜新秩序) which was only limited to the control of China (specially its northern part). Japanese decision-makers conceived that by controlling the resources-filled China alone would make the Empire Japan the paramount super-power in the Asia-Pacific region and create a new geopolitical order in which Japan is the lead Asian country and one of the greatest powers in the world.

The overall vision of "liberating" and controlling the destiny of the European controlled Asian countries was, before 1940, considered idealistic and a long-term goal of Japan. That idea was mostly articulated by ideologues and Japanese political writers, in which some of them (but not all) had close connection with the militarist clique, but the decision-makers never seriously discussed or articulated that vision prior 1940 - that policy came precisely because western powers decided to adopt aggressive policies in trying to make Japan retreat from China.

Lord Fairfax

Ad Honorem
Jan 2015
Space Bat Lair

With Russia dragged into the war the the US now supplying most of Russia's and Britain's needs to defend themselves...
At no point in WWII did the did the US supply "most" of Britain's needs to defend itself, nor for that matter the Soviets.
Jul 2019
Pale Blue Dot - Moonshine Quadrant
I often wonder what would the US response have been if the Japanese had NOT attacked Pearl?
If they had taken Wake and Guam, and the Philippines- but left the US fleet alone and not attacked pearl.... would the US populace have seen That as the last straw to get them on a war footing?
That is an interesting question. FDR certainly was thinking about war early on but he was boxed in by public opinion and his own assertion that the US would not go to war unless attacked.

1933, January 11 – President-elect Roosevelt is thinking heavily about Japan; per FDR cabinet member James Farley in The Roosevelt Years:

"Most of the people in the Philippines are anxious for independence," Roosevelt said, addressing the Cardinal (Patrick Cardinal Hayes), "But before they can be given full freedom, some guarantee of protection must be given them. The Philippines must have security from Japan. After extending herself in China, Japan will be casting her eyes about for new fields of conquest. It is likely she will move Southward and try to extend her possessions along a chain of islands even as far as Australia. Japan will give a lot of concern to the world generally within the next ten years."

1933, Jan 18 - With Roosevelt not yet in office, Raymond Moley wrote in After Seven Years:

On January 18th we [Moley and Tugwell] spent hours with Roosevelt at the 65th Street house explaining, as a starter, why we felt it was a tragic mistake to underwrite the Hoover-Stimson policy in the Far East. Rex, always more fluent and excitable than I, elaborated the argument with all the clarity and passion of which he was capable. I listened intently, trying to discover from F. D. R.'s reaction what had motivated him. We might as well have saved our breath. Roosevelt put an end to the discussion by looking up and recalling that his ancestors used to trade with China. I have always had the deepest sympathy for the Chinese," he said. "How could you expect me not to go along with Stimson on Japan?"

1933, March - FDR's second cabinet meeting on March 7 - just 4 days after his swearing in: “The new President again turned to the possibility of war with Japan...” wrote Cabinet Member James Farley in his book The Roosevelt Years.
per James Farley:

The second Cabinet meeting the following Tuesday was more interesting, because the new President again turned to the possibility of war with Japan. The Japs were swarming in Jehol Province toward the Great Wall of China. There was much discussion of Japan's attitude in the Orient, Japan's clashes with China, and other possible avenues of Japanese activity. The consensus was that, as neighbors, we should exert every effort to keep from getting involved and should make no diplomatic moves which might be so misconstrued as to plunge us into war. There was general agreement that we could defeat Japan by starvation, but that it would take from three to five years to do so.

1940, October 8 - Historian George Morgenstern, using the 1946 Congressional Pearl Harbor Investigation as a source noted that: Roosevelt, at a White House conference, informed Admiral Richardson, commander in chief of the United States fleet and of the Pacific Fleet, that, "if the Japanese attack Thailand, or the Kra Peninsula, or the Dutch East Indies, we would not enter the war; that even if they attacked the Philippines he doubted whether we would enter the war, but that they could not always avoid making mistakes, and that as the war continued and the area of operations expanded, sooner or later they would make a mistake and we would enter the war."

Whether FDR's position was good or bad has, of course, been argued, often at maximum volume, for decades. But it was fairly consistent from the start and his dilemmas were certainly resolved with the attack on Pearl Harbor.


Ad Honorem
Jan 2017
I dunno but if it make sense to do something really dumb might as well go the whole hog
landing troops and taking Hawaii would be downright reasonable