Both World Wars were massive global conflicts that mobilized entire nations and caused immense costs in lives and resources. They featured new, industrialized weapons and tactics like trench warfare in WWI and blitzkrieg attacks in WWII. Both wars also saw totalitarian governments exert control over economies and populations through propaganda, conscription, and restricting civil liberties. Both conflicts included genocide as well, such as the Holocaust in WWII which killed 6 million Jews and 4 million others.