The primary way in which the Hundred Years’ War changed warfare in Europe is that it was the first "total" war, in the sense that all resources were mobilized to fight.
There were actually four HUGE causes for WW1, treaties and alliances brought many countries into war, the imperialism of some countries scared other countries, and they were "defending" themselves, there was a lot of weapons stocking, and countries were creating gigantic armies, and that threatened other countries, and then we have plain old nationalism.
Commanding the U.S. Armed Forces
Effort to decrease the federal budget deficit
