? about WW1?

2.Colonel Edward House informed President Wilson in early 1914 that in Europe “Everybody’s nerves are tense. It requires only a spark to set the whole thing off.” Why was Europe so tense? What deep-rooted underlying factors created this tension? What eventually was the spark that set the ”power keg” of Europe off? What caused this event to happen? Why such a reaction? Could it and the war have been avoided?