World war 2 was the deadliest war on Earth, it killed 70 million people. Most of the countries were mainly involved in some ways and it was fought mainly in Europe. The main causes of the war were the treaty of Versailles and how harsh it was on the Germans. This was because when Hitler was chosen to be their leader, he promised that the country will be great. However, he quickly built an army and steal lands from other countries. They also stormed the Polish. Some other events that happened around ww2 were the Great Depression, Japanese Expansion, Fascism and many other.