who caused WWI?

which is why the first country Britain went to in ww1, was Iraq

A Serbian shoots an Austro-Hungarian, so Germany attacks France.

austria-hungary declares war on serbia
russia declares war on austria-hungary
germany declares war on russia
france declares war on germany
montenegro declares war on austria-hungary
germany declares war on belgium
uk declares war on germany
ottoman empire declares war on russia
japan declares war on germany
italy declares war on austria hungary
portugal declares war on germany
hejaz revolts against ottoman empire
bulgaria declares war on serbia
serbia dies
montenegro dies
romania declares war on austria-hungary
romania surrenders
usa declares war on germany
soviets revolt against russia
russia surrenders
bulgaria surrenders
ottoman empire surrenders
austria-hungary surrenders
germany surrenders

Germany was not exclusively responsible, but they could have diffused the situation with Russia and probably avoided bringing France into the war. Germany definitely did not have to invade France through Belgium, which technically brought Britain into the war.