Before World War 1, Africa and parts of Asia were points of contention amongst the European countries. The increasing competition and desire for greater empires led to an increase in confrontation that helped push the world into World War I.
Over time, countries throughout Europe made mutual defense agreements that would pull them into battle. Therefore, if one country was attacked, allied countries were bound to defend them.
The nationalism of the various countries throughout Europe contributed not only to the beginning but the extension of the war in Europe. Each country tried to prove their dominance and power.