The United States declared war on Japan and Germany on December 8, 1941, following the surprise attack on Pearl Harbor by the Japanese on December 7. Over seventy countries participated in World War II (WWII) in response to Germany’s and Japan’s expansionist policies. Over fifty million people were killed during the conflict. Some scholars suggest that WWII was an extension of World War I (WWI) due to conditions set by the Treaty of Versailles and the hyperinflation of post-WWI Germany. World War II expanded the United States’ role in global politics, helped create the United Nations, and started the nuclear age.