1939年9月1日，德国以闪电战进攻波兰，第二次世界大战正式开始，随后迅速占领了丹麦、挪威、荷兰、比利时和卢森堡等国。1940年，击败英法联军，并占领了法国。随后占领了南斯拉夫和希腊等国。
1941年6月22日，德国开始进攻苏联。1942年冬，斯大林格勒战役开始，德军失利，成为第二次世界大战的转折点。
1944年6月6日，美英联军在法国诺曼底登陆，1945年5月8日德国宣布无条件投降。第二次世界大战结束后，根据雅尔塔协定，苏美英法分区占领德国，柏林作为特殊单位由4国共同管理。1949年5月，美、英、法3国占领区合并，成立德意志联邦共和国，同年10月，苏联占领区宣布成立德意志民主共和国，德国分裂为两个国家。
The history of Germany during World War II closely parallels that of Nazi Germany under Adolf Hitler. Adolf Hitler came to power in Germany in 1933. From that point onward, Germany followed a policy of rearmament and confrontation with other countries. During the war German armies occupied most of Europe; Nazi forces defeated France, took Norway, invaded Yugoslavia and Greece, and occupied much of the European portion of the Soviet Union. Germany also forged alliances with Hungary, Romania, Bulgaria, and later Finland, as well as collaborators in several other nations. The German defeat at the Battle of Stalingrad in 1942 was considered the decisive victory that turned the tide of the war against Germany and her Anti-Cominterm allies. The Second World War culminated in Germany's unconditional surrender to the Allies, the fall of Nazi Germany, and the death of Adolf Hitler.