Why were so many countries involved in World War One?
So many nations were involved because of the alliance system. The Triple Entente (also known as the Allies) were at war with the members of the Central Powers. Countries allied with one another for a variety of reasons, but their association with the alliance involved them in the war. That’s why we can speak of a World War. Wiki has an exhaustive list of each side, I think. Try here: http://en.wikipedia.org/wiki/Allies_of_W… and here: http://en.wikipedia.