On July 28th, 1914, a month after 19-year-old Gavrilo Princip killed Ferdinand, Austria-Hungary declared war on Serbia and invaded, igniting a conflict that would last five years and kill an estimated 17 million people.
But the immediate causes of the war still stemmed from the consequences of the Archduke's killing.
The Cause of WW1
The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary.
When Russia began to mobilize due to its alliance with Serbia, Germany declared war on Russia.
There were many factors that led up to the start of World War I in Europe. ...
The real causes of World War I included politics, secret alliances, imperialism, and nationalistic pride. However, there was one single event, the assassination of Archduke Ferdinand of Austria, which started a chain of events leading to war.
