The causes of the Pearl Harbor was because of rivalry between the United States and Japan.
The causes of WWI:
Treaties and Alliances: In the years preceding WWI many European nations formed alliances that would pull the other into war if one was attacked.
Imperialism: Increasing competition and desire for larger empires led to an increase in hostilities that helped push Europe into war.
Militarism: In the years before WWI began many European nations began stockpiling weapons and building new warships in an arms race.
Nationalism: Much of the origin of the war was based on the desire of the Slavic peoples in Bosnia and Herzegovina to no longer be part of Austria Hungary but instead be part of Serbia. The nationalism of the various countries throughout Europe contributed not only to the beginning but the extension of the war in Europe.
I'm not sure but if you were asking WWI or WWII...So just incase you were asking WWII, it was because the rise of the Nazi Party in Germany and its subsequent invasion of other countries.
