The document summarizes the key causes and events of World War I. It describes the alliance system between the Allied Powers (Triple Entente) of Britain, France, and Russia versus the Central Powers (Triple Alliance) of Germany and Austria-Hungary. The assassination of Archduke Franz Ferdinand of Austria-Hungary by a Serbian nationalist sparked a series of diplomatic and military escalations that led Germany to declare war on Russia, followed by France, and ultimately Britain entering the war against Germany due to their invasion of Belgium. Over 9 million soldiers and civilians lost their lives during the four years of brutal trench warfare and new military technologies on land, sea and air.