<Li> July 25: Tsar approves Council of Ministers decision and Russia begins partial mobilization of 1.1 million men against the Austrian - Hungarian Empire . </Li> <Li> July 25: Serbia responds to Austro - Hungarian démarche with less than full acceptance and asks that the Hague Tribunal arbitrate . Austria - Hungary breaks diplomatic relations with Serbia . Serbia mobilizes its army . </Li> <Li> July 26: Serbian reservists accidentally violate Austro - Hungarian border at Temes - Kubin . </Li> <Li> July 26: A meeting is organised to take place between ambassadors from Great Britain, Germany, Italy and France to discuss the crisis . Germany declines the invitation . </Li>

What is the main cause of world war 1