The events of 70 years ago this week started with a letter from atomic scientist Albert Einstein to President Franklin D. Roosevelt on 2 August 1939 (one month before the beginning of World War II) said in part, “…that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium like elements would be generated….This new phenomenon would also lead to the construction of bombs…single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. …” This was part of what lead to the establishment of the top secret Manhattan Project , the United States’ attempt to develop a weapon before the Third Reich or Japanese Empire did. The beginning of the Atomic Age came in the middle of World War II 72 years ago on a squash court at the University of Chicago when the first controlled nuclear reaction was started as part of the Manhattan Project.
A secret test explosion, code named “Trinity”, occurred at Alamogordo 16 July 1945, overseen by J Robert Oppenheimer. The war in Europe was over, but the war in the Pacific was still in full swing. As Germany was surrendering, the Japanese Empire was still fighting desperately in the Philippines (October 1944-August 1945), Saipan (June 1944), Okinawa (April-June 1945), Iwo Jima (19 February – 26 March 1945), as well as other locations. Japanese units were scattered throughout the Western Pacific as well as in the Japanese Home Islands. The huge number of Allied fatalities in the battles of Okinawa and Iwo Jima concerned Allied commanders that a Normandy-style invasion of Japan proper would result in hundreds of thousands of casualties on both sides. There was no Allied intelligence in Japan itself in 1945—indirect evidence seemed to indicate that the military forces and mobilized civilians would fight savagely for their homeland in the wake of an American and British invasion of Japan and a Soviet invasion of Korea.
The invasion of Japan was being planned throughout the latter part of 1944 and being prepared for in 1945 whilst the atomic weapon was being developed and tested. At the time of the Trinity test, the Allies, particularly the United States and Britain were laying plans for Operation Downfall, which is what the invasion was to be called. The first part was to be the invasion of Kyushsu Island (southeastern Japan), dubbed “Operation Olympic”,scheduled for 1 November 1945, followed by “Operation Coronet”–the planned invasion of Honshu (the island on which Tokyo is located) on 1 March 1946.
President Truman was with Winston Churchill and Josef Stalin planning the disposition of the vanquished Germany and discussing policy toward still-belligerent Japan when the President was informed about the success of the Trinity explosion. Historian Eiji Takemae reports in Inside GHQ (p. 40) that the President was told, “baby satisfactorily born” after the test, and the President told Prime Minister Winston Churchill on 17 July that the Trinity test was successful. The two leaders issued “The Potsdam Declaration” on the 26th calling on the unconditional surrender of Japan to the Allies. Orders were given to warn the Japanese that failure to surrender would cause “utter destruction of the Japanese homeland.” Naval and air bombardment increased on places like Tokyo.
Whilst planning for the invasion continued, the Manhattan Project continued with development of an atomic bomb as a means to win the war; with the defeat of Germany in May of 1945, this effort, like the rest of the war effort went into the defeat of Japan. Strategic bombing, or bombing of the enemy homeland, which had been so effective in Europe against Germany, would be used to prepare for Downfall. However, the explosive force of the Trinity prototype had been greater than expected. A whole army unit, the 509th Composite Group, which consisted of bomber, air transport, and ground units was formed and commanded by Colonel Paul W. Tibbets, who had already distinguished himself as a B-17 pilot over Europe. The unit was originally based at Wendover, Utah, but was moved to Tinian with the express mission of delivering the atomic bomb on up to four Japanese cities: Hiroshima—a major army base, manufacturing and communications centre, Kyoto (an intellectual centre removed from the final list), and Niigata (seaport, petroleum centre, and site of a relocation camp).. Nagasaki—a major seaport and ship building was an alternate target for Kokura– location of large military arsenal
Meanwhile, the USS Indianapolis (CA-35) received a top secret cargo to be delivered to Tinian Island, where it would be loaded onto a B-29 Superfortress bomber. This was the “Little Boy” nuclear device to be dropped on Hiroshima on 6 August 1945, 70 years ago this week. Little Boy was built with a “gun-type” method of producing a critical mass, or the minimum amount of fissile material needed to maintain a nuclear chain reaction: it shot one 1 lb mass of uranium U-235 into another 1lb mass of U-235 to produce its explosion—an explosion that almost totally destroyed an industrial city and killed over 100,000 people.
The Hiroshima bombing mission was commanded by Colonel Tibbets. His B-29, the Enola Gay, was named after his mother. The mission consisted of the Enola Gay and her crew of 12, and an observer aircraft. The flight left Tinian at 2:45am local time, and arrived Tokyo at 8:15am. Little Boy was delivered then, and the flight returned at 14:58 (2 minutes before 3pm) to a hero’s welcome. Tibbets received the Distinguished Service Cross, and the other crew members received the Air Medal.
The second raid was executed by Major Charles W. Sweeny flying a B-29 dubbed “Bock’s Car” on 9 August 1945 flying from the same airfield as the Enola Gay. Sweeney had flown in the Great Artiste, the observation airplane that accompanied Col. Tibbet’s aircraft three days before. The bomb Sweeny dropped was “Fat Man” a bomb that used plutonium rather than uranium as the energy source. Fat Man used an implosion detonator to bring the plutonium to critical mass. The implosion detonator was more sophisticated than the gun-type used in the Hiroshima bomb.
Both cities were leveled by the two explosions. Estimates vary, but about 135,000 people died at Hiroshima and 64,000 at Nagasaki. The differences are often attributed to the terrain of the two cities: Hiroshima was in a plain and Nagasaki was surrounded by mountains. Each city was attacked by a single aircraft (with another observation aircraft flying in formation). In comparison, the firebombing of Tokyo on 9-10 March 1945 involving 334 B-29s flying at low altitude and killing between 80,000 and 200,000 people on the ground.
The bombings left legacies. People continued to die from radiation poisoning months after the attacks. The Union of Soviet Socialist Republics (USSR–often erroneously called “Russia”) declared war on Japan on the 8th of August—two days after the Hiroshima attack, and one day before the Nagasaki attack. This caused Japan to lose any claims to Manchuria and cause the lost a part of the Kurile Islands. The major opposition to surrender in the Supreme War Council collapsed and Emperor Hirohito announced the Japanese surrender on 15 August. Japan banned nuclear weapons and is a major proponent of nonproliferation. Japan has become a democratic monarchy like Great Britain, Sweden, and other countries. Hiroshima and Nagasaki have peace memorials. Eight other countries now have atomic weapons: USA (1945), USSR (1949), United Kingdom (1952), France (1960), Peoples Republic of China (1964), India (1967), Pakistan (1998), and Democratic Peoples Republic of Korea (2006). Israel is reported to have several warheads, and Islamic Republic of Iran is said to be developing them. Since 1945, no nation has used nuclear weapons against another nation.