Date : 28 July 1914 – 11 November 1918 

Duration : 4 years, 3 months and 2 weeks

The World War I was caused by several underlying factors. However, the main trigger was the assassination of Archduke Frank Ferdinand. The war fought for four years saw the death of over 17 million people.

Here are seven key causes of the World War I :

The Assassination of Archduke Ferdinand

The assassination of Archduke Franz Ferdinand of Austria, the heir presumptive to the Austro-Hungarian throne was the main cause of the war. A group called Gavrilo assassinated the prince during a visit to Sarajevo. Since members of the group were Bosnian Serbs, the Austria-Hungary declared a war on Serbia. Serbia at the time was in alliance with Russia so had the Russians backing. This also led German to declare war against Russia.

The Lack of International Laws

Lack of international treaties and laws was another cause of the World War I. Unlike today, there were many laws governing the world at that time. No laws at the time restricted the occupation of territories and declaration of war on another country.

The Existence of Alliances

The existence of alliance to enhance defence was another cause of the World War. Prior to the war, Serbia had an alliance with Russia while German was Austria-Hungary. So after the assignation, Russia went in support of Serbia and Germany also backed Austria-Hungary. Both Russia and German also had alliances with other nations in Europe, and that spread the war.

The Balkan War

The instability of the Ottoman Empire had also created a vacuum in the region. This resulted in the Balkan War with Serbia, Greece, Bulgaria, and Montenegro standing up against the empire. Their victory became a shock to other countries with Russia, France and Britain taking advantage to annex some areas. This worsened the situation and contributed to the war.


Due to the instability in the Slavic region caused by the Balkan war, Bosnia and Herzegovina tried to take advantage of its merge with Serbia. These countries were part of the Austria-Hungarian Empire. This created a series of attacks between the countries, increasing the possibilities of the war.


The expansion of colonies by the major European powers became obvious due to struggle for raw materials. Britain was in control of South Asia, France in Africa and Spain in South America. Their aim to expand these colonies created conflicts among them. This would later contribute to the World War I.

The Fallout of the Ottoman Empire

The last point that contributed to the World War I was the fall in power of the Ottoman Empire. The once powerful empire became weaker due to internal conflicts. This was what led to the Balkan war and increased the tension between Serbia and the Austria-Hungary.

Major Periods in World History