Unlike its predecessor, World War II didn’t start because of the assassination of a significant leader, thankfully. However, we can pinpoint its spark to both recurring and new causes alike. Some of them are similar to WWI’s, such as militarism and imperialism but others are unprecedented like economic downturns and the rise of a new type of leader: totalitarianism. However, World War II, or WWII, was a global war that was clearly underway by 1939 and ended sharply in 1945. It involved a vast majority of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, with more than 100 million people serving in military units. In a state of "total war", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Marked by significant events involving the mass death of civilians, including the Holocaust and the only use of nuclear weapons in warfare, it resulted in 50 million to over 70 million fatalities. These deaths make World War II the deadliest conflict in all of human history.