Unknown, really. Most agree that Japan felt the trade embargo that the US imposed on Japan was looked upon as an 'act-of-war' by the Japanese hierarchy. The Japanese military men were very ashamed of themselves and their country once they learned that the Japanese Government had not declared war on the US - even though they had asked the Russian government to pass that information on to the US. The Russians didn't do so, because they were hoping to invade/take over Japan during the war. (I'm sure someone will edit this for clarity/content, but it's a heckuva start! :)
cause
Pearl Harbor.
The attack on Pearl Harbor by the Japanese Military.
Question is rather ambiguous. Pearl Harbor is a Naval base located in our 50th State Hawaii, not a cause. Please rephrase the question.
The attack on Pearl Harbor
Elimination of the US Battlefleet stationed at Pearl Harbor.
He allowed Japan to attack the US at Pearl Harbor, Hawaii
What actually cause them to join the war was the attack on Pearl Harbor
Yes The Attack on Pearl Harbor was the reason that the USA went to war with Japan at the same time Germany declared war on the USA.
The attack on Pearl Harbor caused the US to declare war on Japan and then Germany and Italy. 1,177 crewman died that day.
2 hours or so after the attack, President Roosevelt declared war on Japan, which lead to their destruction.
He allowed Japan to attack the US at Pearl Harbor, Hawaii