Causes of World War One

Archduke Ferdinand being ambushed
Assassination of Archduke Ferdinand

Introduction - Causes of WW1

Many kids learn in their history books that the assassination of Archduke Franz Ferdinand of Austria-Hungary in June of 1914 is what started World War One. This was indeed the spark that ignited the war however the answer to the question of what caused World War One is much more complicated than that. On this page we list facts about the main factors that led to the outbreak of the First World War with links to more detailed pages of each cause.

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As you read about the root causes of World War One below you will see that the situation among the major European countries was set for catastrophe. It wasn't really a question of if there would be a war but rather just of how and when it would start. The consequence was a horrible conflict that saw death and destruction on a scale never seen before.

List of Major Causes of World War One

Information about the Causes of World War One

Mutual Defense Alliances

In the decades leading up to World War 1 the major military powers in Europe made numerous alliances. These alliances were mutual defense agreements where the countries would agree if either was attacked the other would come to its defense. If it had not been for these alliances WW1 might have just been a relatively minor conflict between Austria-Hungary and Serbia.


Before World War One many of the European countries were on a quest to expand their empires in order to increase their power and wealth; they sought to acquire new territories especially in Asia and Africa. The competition for these new lands, often rich with desired natural resources, led to friction between these mighty countries which would be a major factor as to why World War One started.


Prior to the outbreak of WW1 the citizens of the major European military powers had strong feelings of patriotism mixed with feelings of superiority over the other European countries. This in a way made them almost anxious to go to war to prove their superiority. These feelings all helped extend the war by making negotiations to end it less desirable due to the possible appearance of weakness.


The early 1900s saw a major increase in military power in many of the European countries along with the willingness to use this military power to promote their countries interest. This militarism would be a major cause of World War One and the main reason the war was so deadly. Germany's military power grew immensely from 1900 to 1914 and Great Britain had a tremendous increase in its naval power.

Bosnian Crisis of 1908

In 1878 Austria-Hungary occupied Bosnia and Herzegovina which had been part of the Ottoman Empire. This caused years of friction between Austria-Hungary, Serbia, and the Slavic peoples in Bosnia and Herzegovina who did not want to be controlled by Austria-Hungary. In 1908 matters worsened when Austria-Hungary annexed Bosnia and Herzegovina officially making them part of their empire. This is called the Bosnian Crisis of 1908.

Assassination of Archduke Franz Ferdinand

Last on our list of the Causes of World War One is the event that triggered the war and brought all the other reasons into play. The assassination of Archduke Franz Ferdinand, who was the heir to the Austro-Hungarian throne, occurred on June 28th 1914 in Sarajevo. The assassin was Gavrilo Princip who was part of a group who wanted certain provinces under Austria-Hungary's rule to be given to Serbia. This led to Austria-Hungary making certain demands on Serbia and then finally to the outbreak of war.