World War II also known as the The Second World War, was a global war that lasted from 1939 1945, though related began earlier. It involved the 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, and directly involved more than 100 million peop;e from over 30 countries. In a state of "total war", the major participants threw their entire economic, industrial and scientific capabilities War Effort, erasing the distinction between civilian and military resources.