World War II

World War II was fought from 1939 to 1945 between the Allied Powers, led by the United Kingdom, the Soviet Union and the United States, and the Axis Powers, led by Germany, Italy and Japan. It killed an estimated 70 to 85 million people, including about six million Jews murdered in the Holocaust. It ended with unconditional Axis surrenders in Europe in May 1945 and in the Pacific in September 1945, after the United States used atomic bombs on Hiroshima and Nagasaki.

The settlement that followed created the United Nations and the Bretton Woods institutions, the framework of international law and multilateral finance still in use. It also set lasting national habits. Germany has not joined an offensive operation outside a NATO or UN framework since 1945, a line Berlin held when it ruled out joining the Iran campaign in March 2026.

The war remains the benchmark for scale. On 20 March 2026 the US commander ADM Brad Cooper called the destruction of more than 130 Iranian naval vessels the largest naval attrition campaign in three weeks since World War II. On 2 August Donald Trump promised Iran force "not seen since World War II", then called off the strike within hours.