Who and/or what caused World War 1

I think that all the European countries together caused the war because. . .
         -All of the countries were arguing that they should have/own more land.
         -There was much retaliation between each country.
         -Leaders in each country were not trying to prevent the war like they should have.
         -Everyone disregarded each countries defined destiny.
         -Both groups mobilized there troops in certain ways to make the other countries mad, and again make them want to retaliate.
         -The countries were basically tempting each other to go to war by buying so many new weapons.
         -When all of the countries in Europe kept imperializing, the relations between the countries worsened causing hatred to form among the countries.