Dropping the Atomic Bomb
Little Boy and Fat Man
Little Boy was the first nuclear weapon used in warfare. It exploded approximately 1,800 feet over Hiroshima, Japan, on the morning of August 6, 1945, with a force equal to 13,000 tons of TNT. Immediate deaths were between 70,000 to 130,000.
Little Boy was dropped from a B-29 bomber piloted by U.S. Army Air Force Col. Paul W. Tibbets. Tibbets had named the plane Enola Gay after his mother the night before the atomic attack.
Fat Man was the second nuclear weapon used in warfare. Dropped on Nagasaki, Japan, on August 9, 1945, Fat Man devastated more than two square miles of the city and caused approximately 45,000 immediate deaths.
Major Charles W. Sweeney piloted the B-29, #77 that dropped Fat Man. After the nuclear mission, #77 was christened Bockscar after its regular Command Pilot, Fred Bock.
While Little Boy was a uranium gun-type device, Fat Man was a more complicated and powerful plutonium implosion weapon that exploded with a force equal to 20 kilotons of TNT.
Truman Takes Office
Three weeks before the German surrender, President Roosevelt died. When Harry Truman took office on April 12, 1945, he knew little of the Manhattan Project or the atomic bomb. He was quickly brought up to date on the project and its progress. It now became his decision to drop the atomic bomb or launch an invasion of the Japanese homelands.
Plans for the Invasion of Japan
By May 8, 1945, Victory in Europe day, the surrender of the Germans freed battle-weary troops for duty in the Pacific. The U.S. began planning the long- anticipated invasion of the Japanese mainlands. According to U.S. military officials, a Japanese invasion would have to be a two-phase invasion involving two million American soldiers. The invasion was estimated to take six months and cost tens of thousands of lives on both sides.
Some estimates put the number of potential American casualties as high as a million, although the numbers are still debated today. The Joint Chiefs of Staff believed an invasion of Japan would be bigger than any other campaign of WW II - even more costly than the Normandy landing, which cost 220,000 American casualties. They estimated they would lose 31,000 men in the first 30 days alone. Considering that the U.S. suffered 40,000 American casualties taking the island of Okinawa alone, this estimate seemed conservative.
The Japanese were also preparing for the invasion, which they called The Battle for the Homeland. They trained women and boys as young as nine to fight with bamboo spears. According to the Japanese military, every man, woman and child would fight to the death rather than surrender.
The Decision
On July 16, 1945, Truman was notified of the successful atomic bomb test at the Trinity Test Site while at the Potsdam Conference in Berlin. Although Truman discussed the new weapon with Churchill and Stalin, the decision to use it was his alone.
Japan was near defeat. Its air force was in shambles, allowing American aircraft to attack Japanese cities at will. A single fire bomb raid on Tokyo in March 1945 had killed nearly 100,000 people and injured over a million. A second air attack on Tokyo in May killed another 83,000. By summer, Tokyo was in ruins. Meanwhile, the U.S. Navy had cut the islands' supply lines. Still, the Japanese vowed to fight on.
Because of the Japanese Bushido Tradition it was believed that the Japanese would fight to the bitter end, a long and costly invasion of the home islands seemed unavoidable, unless Truman used the atomic bomb.
Japan had never been defeated or invaded in its entire history. As Japan grew more desperate, so did its military tactics. The Japanese had launched 560 Kamikaze raids since May, sinking 40 U.S. naval vessels. U.S. military officials believed the U.S. would pay a heavy toll for every inch of Japanese territory gained. The long and bloody island hopping campaign was proof. It had taken hundreds of thousands of American lives already, just to position the troops within striking distance of the Japanese mainlands.
Potsdam Proclamation
On July 16, 1945, at the Big Three conference at Potsdam, the U.S., the Soviet Union, and Great Britain drafted the Potsdam Declaration, telling Japan to surrender unconditionally or face "prompt and utter destruction."
Japan had begun to open talks with Russia in an attempt to negotiate peace, but they would not accept unconditional surrender. An unconditional surrender would have removed the Emperor and humiliated the Japanese warrior tradition of honor. The Japanese rejected the offer on July 29, 1945.
In late May 1945, a committee of military officers and Manhattan Project scientists chose Kokura Arsenal, Hiroshima, Niigata and Kyoto as potential targets for the atomic bombs. They believed that attacks on these cities, none of which had been bombed before, would have a profound psychological effect on the Japanese. Kyoto was later removed from the list because of its cultural and historical significance, and Nagasaki was added in its place.
The U.S. Army Air Force' 509th Composite Group was ordered to attack Hiroshima, Kokura, Niigata or Nagasaki anytime after August 3rd, as soon as weather permitted.
The Targets
Hiroshima
Hiroshima was chosen as the primary target because it was the only city on the list that did not contain American prisoners of war. It was also an important military and communications center with a population of 300,000.
On August 6, 1945, the B-29 Enola Gay, piloted by Col. Paul Tibbets, flew at low altitude on automatic pilot toward its target 1,500 miles away. Just before reaching its target, the aircraft climbed to 31,000 feet. After releasing Little Boy, Tibbets immediately banked sharply away to avoid the anticipated shock waves of the blast. A huge explosion lit the morning sky. When the bomb exploded, the Enola Gay was already 11.5 miles away, yet the shock wave from the explosion rocked the aircraft. Tibbets and crew thought they had been hit by anti-aircraft fire, then a second shock wave hit the plane.
"There was the mushroom growing up, and we watched it blossom. And down below it, the thing reminded me more of a boiling pot of tar than any other description I can give it. It was black and boiling underneath with a steam haze on top of it. And, of course, we had seen the city when we went in, and there was nothing to see when we came back. It was covered by this boiling, black-looking mess."--Col. Paul Tibbets
Nagasaki
Within hours of the Hiroshima attack, President Truman warned that if the Japanese still refused to surrender unconditionally, the U.S. would attack again. But the Japanese still did not surrender unconditionally.
On August 9, 1945, the B-29 called Bockscar, flown by Major Charles Sweeney, took off from Tinian on its way to drop the second atomic bomb on its primary target, Kokura Arsenal.
The second atomic bomb mission came close to being a disaster. First, a fuel pump malfunctioned. Then bad weather made it impossible to visually bomb the primary target with any accuracy, so Sweeney headed toward his secondary target: Nagasaki. Nagasaki was the home of the Mitsubishi Steel and Arms Works plant. But it, too, was under cloud cover. With minimal fuel left, a small break in the cloud cover suddenly made visual bombing possible, and Fat Man was released.
Because Bockscar had continued past Kokura to its secondary target Nagasaki, it almost ran out of fuel on its return trip and had to make an emergency landing on Okinawa
The Aftermath
Hiroshima: August 6, 1945, the uranium bomb, Little Boy, exploded at 8:16 a.m. Hiroshima time, 43 seconds after it left the B-29 Enola Gay, almost 2,000 feet above the ground. It had a yield equivalent to 20,000 tons of TNT. Everything within four square miles was destroyed.
Instantly Killed:
70,000
Instantly Injured:
70,000
December 1945 total death toll:
140,000
1950 total death toll:
200,000
Nagasaki: August 9, 1945, the plutonium bomb, Fat Man, exploded 1,650 feet above Nagasaki at 11:01 a.m after it left the B-29 Bockscar. It had a force of 21,000 tons of TNT. Everything within three square miles was destroyed.
Instantly Killed:
40,000
Instantly Injured:
60,000
January 1946 total death toll:
70,000
1950 total death toll:
140,000
The bombing of Hiroshima and Nagasaki caused just a fraction of the casualties of WW II. The March 1945 fire bomb raid on Tokyo killed nearly 100,000 people and injured over 1,000,000, and the May 1945 fire bomb raid killed another 83,000. The total death toll of World War II for both Allied and Axis nations is estimated to exceed 55 million, more than half civilian.
Note: These are the official statistics quoted in a 1994 U.S. Department of Energy document. Other organizations have conducted continuous studies of their own, and continue to debate the statistics.