Actually, Gavrilo Princip was only the detonator for the bomb that was the war. The anglo-german naval race, fueled by Alfred Thayer Mahan's "The influence of sea power upon history", then we have the innate rivalry between France and Germany, then we have political issues in Russia, Italian reclamations of Austro-Hungarian territory, colonial disputes...
Proving you need to dig deeper. No offense meant, just wanted to correct an error on your part