Question

what was the main reason to start 1st world war?write in one sentence.​

Answer 1

the murder of Austrian prince Francis Ferdinand of Austria was the main reason.

as the Duke was going g to Serbia with his wife he was attacked by a Serbian gang who shot him and hence killed him. when Austria gave an ultimatum to Serbia blaming them for the murder on june 28 1914 Serbia didn't paid any attention to the ultimatum thus Austria were left with no alternative but to attack Serbia on July 28 1914 and hence started the first world war

Answer 2

the main reason to cause WW1 was the assassination of archduke Franz Ferdinand at Sarajevo on 28 June 1914.