Map of World with Participants in World War I :

Allies- in green

Central Powers- in orange

Neutral- in grey

The triggering event cause of World War I was the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, in 1914. The fact that the assassination did not lead to a war of two nations, but a war among many nations around the whole world, has to do with the alliance system in the era. Although the actual causes of the war are complicated, the escalation of the size of the war can be partly attributed to the alliance treaties.

For the readers’ convenience,  some of the entrances of the participants will be listed below:

1. Austria-Hungary- declared war on Serbia due to the assassination.

2. Serbia- became a participant by Austria-Hungary’s war declaration.

3. Russia- allied to Serbia by their treaty

4. Germany- allied to Austria-Hungary by their treaty

5. France- allied to Russia

6. Britain- allied to France. Since Britain has entered the war, her many colonies have became participants, whether with direct military support or financial support.

7. Australia, Canada, India, New Zealand, and the Union of South Africa- entered the war because of their ties with Britain

8. Japan- entered the war due to its treaty with Britain.

As we can see, over 10 additional nations were involved because of their alliance treaties with other nations. Although some nations have entered the war with reasons of their own, it is undeniable that the alliance treaties were strong factors for the escalation of the war to a world-wide scale.