What Was the Underlying Cause of World War 1? World War 1 was caused by alliances, more specifically World War 1 was a big fight that was started for a very poor reason. WW1 started on July 28, 1914. With the assassination of Franz Ferdinand (Archduke of Austria-Hungary), Austria-Hungary wanted revenge for the assassination. So, they commanded Serbia to give up the people who were apart of the crime. Of course no nation will bow down to such a command, so, Austria-Hungary wanted to declare war on Serbia and Russia had Austria-Hungary’s back. What was the main source of WW1? Alliances was the underlying cause of WW1. On August 5, 1914 The Chicago Daily Tribune published a propaganda cartoon by an artist named John T. McCutcheon. This cartoon