Nazi Germany

The atomic bombings of the cities of Hiroshima and Nagasaki in Japan were conducted by the United States during the final stages of World War II in August 1945. The two bombings were the first and remain the only use of nuclear weapons in wartime.
Following a firebombing campaign that destroyed many Japanese cities, the Allies prepared for a costly invasion of Japan. The war in Europe ended when Nazi Germany signed its instrument of surrender on May 8, 1945, but the Pacific War continued. Together with the United Kingdom and China, the United States called for the unconditional surrender of the Japanese armed forces in the Potsdam Declaration on July 26, 1945, threatening "prompt and utter destruction".
By August 1945, the Allied Manhattan Project had successfully tested an atomic device and had produced weapons based on two alternate designs. The 509th Composite Group of the U.S. Army Air Forces was equipped with Silverplate Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. A uranium gun-type atomic bomb (Little Boy) was dropped on Hiroshima on August 6, 1945, followed by a plutonium implosion-type bomb (Fat Man) on the city of Nagasaki on August 9. Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki; roughly half of the deaths in each city occurred on the first day. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness. In both cities, most of the dead were civilians, although Hiroshima had a sizeable garrison.