How did Japan get involved in World War 2?

They had been planning for months and months, the Japanese were allied with Italy and Germany - and taking over the US with its land and resources sounded like a good idea. December 7, 1941 they attacked by sea and air at Pearl Harbor killing over 2,400 soldiers and civilians. The USA declared war on Japan December 8 and on December 11 Germany declared war on the USA putting us at war on two fronts. The previous response is technically correct, at least from the viewpoint of the USA. The bigger picture however, needs to be reviewed for a more complete understanding.

Comment: the above is completely wrong and largely made up. Example: other than a couple of midget submarines, there was no 'Sea' attack on Pearl. The following is very accurate. A kudos to whomever posted it:

Japan was opened to the modern world only late in the 1800's. Previously Japan had been a middle ages styled feudal society. They quickly modernized and were successful in two major campaigns in the early 1900's. First they handily beat the Russians in the Manchurian arena, giving them a more or less free hand for thirty years in China. During WWI, 1914-1918, the Japanese took over the German Pacific island colonies. Using these two events as a springboard the Japanese became more and more aggressive. Korea, Formosa and north China were occupied next. The militaristic Japanese leadership desired an ultimate goal of a great eastern Asia empire stretching from Java to Siberia with Tokyo as its capital.

When the fantastic and unexpected German victories in Europe occurred in 1939, 1940 and 1941 (against Britain, the Netherlands, France and Russia - all colonial powers in the east Asia area) the Japanese leadership could count only one obstacle to further expansion - the USA. The reason the USA was in the way was due to the USA colonial empire in the far east (Philippines - These islands were an American colony since 1900 when they were forcibly taken from Spain. Afterwards a long and brutal war was fought against the Phillipinos who desired independence. By 1940 the islands had been 'pacified' more or less and were docile towards American occupation). The American colony was situated in the middle of the Japanese sphere and posed a threat to all movements by the Japanese navy. As such they had to be eliminated.

What immediately precipitated the Japanese to attack the USA at Hawaii and the Philippines was the USA led embargo of oil and other supplies to Japan. This declaration of 'economic' war by the USA triggered the Japanese to immediately advance their war plans.

The point of all this is that Pearl Harbor may be the 'start' of WWII in the Pacific from the USA standpoint, but truth is it had been going on for forty years as far as Japan was concerned. The war with the USA only meant one more beligerent for the Japanese who were essentially at war with all their neighboring countries and territories since 1900. I should add that neither the Japanese or Germans ever had any intention of 'taking over' the USA land or resources, despite what the top poster has stated.

The German war in Europe was fought mainly to secure Germany against Russian aggression and expansion. Ultimately the Germans hoped to be powerful enough to act as a balancing factor against looming American power. Of course, Germany lost and Russian aggression and expansion ensued unabated, leading to decades of war (hot and cold) between them and the USA (Berlin, Korea, Vietnam, Angola, Cuba, Afganistan - just to name a few).

The Japanese war aims were as I outlined above, to secure a great eastern Asia empire at the expense of the western nations empires in the same area. Japan never had war aims of taking over California or any other American territory.

Anything you've heard to the contrary is propaganda, much of it put out by Churchill's people who desperately desired to draw the USA into the war in order to help secure Britains place in the world. As for Britain, it's a classic situation of 'better be careful what you wish for'. Britain did get the USA into the war but the war cost the British their empire, much of their wealth and almost all their leadership in world events. Great job! As I see it, they didn't "get involved." They initiated hostilities themselves by occupying real estate that was not their own. They began invasions of other countries years before it was called a "World War."

Japan Declared war on China in WWII, taking over half the country. Japan also had an Alliance with Germany. After declaring war on the US (Pearl Harbor), Germany Declared war on the US, hoping Japan would invade the USSR (Russia). But Japan had secretly signed a non-agression treaty with the Soviet Union. -Feewet they got involved with the united states when they dropped a bomb on pearl harbor with fighter planes.