What role did objective and subjective factors play in the origin of the First World War?

30 years of peace is too much and all the ripening contradictions in relations between the leading countries of Europe could not but result in a new imperialist war. Each country had a pretext for war: Russia sought to gain a foothold in the Balkans, France to return Alsace and Lataryngia, lost during the Franco-Prussian war, Germany to provide itself with colonies. Two military blocs are created: the tripartite alliance and the Entente, and then Austria-Hungary, incited by Germany, declares war on Serbia, based on the events in Sarajevo.