Next, think more about the four main causes of world war i. which cause do you think had the biggest impact on starting the war? which one had the least impact? in the space provided, rank the causes from one to four in a list. number one should be the cause that had the biggest impact. number four should be the cause you think was had the least impact. feel free to look back through the lessons in this unit or research the topic on the internet to you with your ranking