Answer:
Russia mobilizing its forces on Germany's eastern borders was the event that made Germany declare war on the allies.
Explanation:
- The killing of Archduke Franz Ferdinand by the serbian nationalist Gavrilo princip was the trigger that started world war.
- The alliance system was an important factor that caused world war 1 as, any countries who were in alliance had to help the other country if a war broke out.
- In World War I, two major alliances faced each other.
- The two major alliances that fought for the power of Europe were : Allied power that includes Russia, Britain and France and the Central Powers(Germany, Austria-Hungary).
