World War II began because of the unsettled differences between all the countries. The United States wanted to remain neutral but ended up in total war with all the other countries. The war was a total war which is that the war was all out many soldiers dying and getting injured. None of the countries were in the economic stable enough to have WW II because WW I had not ended not that long ago. Many countries were involved and most of the Genocides happen between this time. After many years of war it all ended in 1945 that is also when the Holocaust ended. Many leaders were arrested because of Slave Labor and Hitler committed suicide before they found him. The fail of the Treaty of Versailles. Also the fail of the league of nations.