Nationality is not the same thing as ethnicity . I ' m not sure why so many people have trouble grasping this . <| sep |> Please tell us why on earth the employees did what they did <| sep |> But the circumstances would have been different . Europe was a mess at that time and a lot of incidents would have sparked the war , but because it was this one , Austria declared war on Serbia , their ally Russia declared war on Austria , and that led to Germany declaring war on Russia and their ally France . The UK , which more leaned toward staying neutral or joining Germany in case of a war , decided to side with France to punish Germany for steamrolling Belgium to get around the French defenses . I simplified a lot , but still If it wasn ' t for Princip , it ' s unlikely Germany would have felt forced into the role of the aggressor , which allegedly changed the role of the UK . We would have had a much different outcome .