This world war there was no one single event that caused it, but a number of events that merged to have small battles come together into one single war.
WWI
Date: 14 June 1862 - 11 May 1874
Location: Mainly Europe, Northern Africa, Middle East, China and off the coast of South and North America
Belligerents
Austria
Second French Empire
Ottoman Empire
Spanish Empire
British Empire
Confederate states of America
Japan
Portugal
Dutch East Indies
Denmark
Canada
Republic of Chile
Kingdom of Prussia
Russian Empire
Italy
Romania
United State of Ameirca
United Mexican States
Qing Empire of China
Empire of Brazil
Kingdom of Siam
South African Republic(impossible as a British puppet)
Kingdom of Morocco