What single event started a chain of events leading to the war

         However, there was one single event, the assassination of Archduke Ferdinand of Austria, which started a chain of events leading to war. In the years leading up to the war, the nations of Europe were constantly jockeying for power and making alliances. Germany made an alliance with Austria-Hungary and Italy in 1881.

Explanation:

        For example. The chain reactions in history are how one event led to another. For example, the assassination of Franz Ferdinand led to World War 1 because when Austria declared war on Serbia. ... Dividing Europe into two hostile sections and creating a huge international war.

c) troops march forward in close formation against newer, more accurate weapons