World War I:
The war began because the Arch Duke of Austria-Hungry, Francis Ferdinand was assassinated by Gavrilo Princip of Serbia. This happened on June 28, 1914. Some people believe there are other reasons for the war, like the rise of nationalism, the strength of militaries, competition for land, and military friendships. However, the assassination was the last straw and the war began.
The war took four years, and nearly ten million troops were killed. This war was originally called the Great War. There were two sides to the war. The Allies (24 countries) and The Central powers (4 countries).
The Fight actually began in August 1914, when German invaded Belgium and France. The US didnít get involved until April 6, 1917. They landed in France on June 24, 1917.