The reason that WWI started was because tension rose between Austria-Hungary and Serbia. Both of them wanted the territory of Bosnia and Herzegovina.
This is the beginning of WWI and soldiers on both sides are digging trenches to stay in during snow and rain. This also helps protect them from harm.
German U-boats began to attack American ships. The Americans warned them to stop but the Germans ignored them. As a result the Americans joined the Allied Forces
The Allied forces now won the war in 1918. There are a total of 8.5 soldiers killed and 20 million wounded.
Us soldiers now came up with a treaty. It is called the Treaty of Versailles and we had Germany do some things that we told them to do and they had to take the blame for starting the war.
WWI had caused a great hardship for people but in the end Austria and Hungary became separate countries, Poland and Czechoslovakia gained independence, and Finland, Estonia, Latvia, and Lithuania, became independent.