At 3:49 a.m. on 9 August, Boeing B-29 Superfortress bomber Bockscar (sometimes written as Bock's Car), commanded by Major Charles Sweeney, departed Tinian. It was followed by a second B-29 as scientific observer and a third as photographic observer. The Bockscar carried a plutonium nuclear-fission bomb nicknamed "Fat Man" that was 10 ft 8 inches long and 5 ft in diameter, with a payload greater than that of the Hiroshima bomb. The plutonium 238 isotope core consisted of two melon-shaped hemispheres surrounded by a ring of explosive charges designed to drive the sections together, achieving "critical mass" and a chain reaction releasing 22 kilotons of energy in one-millionth of a second.
Sweeney flew to Kokura but found it overcast and circled for 10 minutes. Despite the clouds, bombardier Kermit Beahan believed they could bomb visually. Sweeney, concerned about a faulty valve that limited fuel, decided to divert to Nagasaki, which was also partly obscured by clouds. Beahan believed he could bomb by radar, but a break in the clouds allowed him to bomb visually, using the Mitsubishi shipyards as his aiming point.
The Bockscar released the bomb from 31,000 ft at 11:02 a.m. local time. The bomb detonated 53 sec later, approximately 1,500 ft over the city, destroying everything within a 1,000 yd radius. An intense blue-white explosion pushed up a pillar of fire 10,000 ft, followed by a mushroom cloud to 60,000 ft.
Although the bomb missed its intended aiming point by 8,500 ft, it leveled one-third of the city. Called the "Red Circle of Death," the fire and blast area within the Urakami Valley section destroyed more than 18,000 homes and killed 74,000 people. Another 75,000 were injured, and many later died from wounds or complications. Blast forces traveling in excess of 9,000 mph damaged buildings 3 mi away, and the concussion was felt 40 mi from the epicenter. "Ashes of Death" from the mushroom cloud spread radiation poisoning, killing all who were not killed outright within 1,000 yd of the epicenter. The bomb might have killed thousands more, but it detonated away from the city center in a heavy industrial area, vaporizing three of Nagasaki's largest war factories but "minimizing" deaths.
Sweeney made one complete circle of the city to determine damage and then left after fuel concerns and heavy smoke made other circuits futile. Critically low on fuel, he flew to Okinawa, landing at Yontan Field about 12:30 p.m., his gas tanks virtually empty. After refueling, Bockscar flew to Tinian, arriving there at 10:30 p.m. local time after a 20-hour flight.
Included in the instrument bundle dropped from the observation plane was a letter addressed to Japanese physicist Professor F. Sagane that urged immediate surrender and threatened continued atomic destruction of Japanese cities. Written by three American physicists, the letter was a bluff, as no other atomic bombs were then ready. Nonetheless, the second atomic attack, coupled with the 8 August declaration of war by the Soviet Union, provided Japanese Emperor Hirohito with the excuse to end the war. Mark Van Rhyn
Chinnock, Frank W. Nagasaki: The Forgotten Bomb. New York: World Publishing, 1969.; Ishikawa, Eisei. Hiroshima and Nagasaki: The Physical, Medical, and Social Effects of the Atomic Bombings. Trans. David L. Swain. New York: Basic Books, 1981.; Nobile, Philip. Judgment at the Smithsonian: The Bombing of Hiroshima and Nagasaki. New York: Marlowe and Company, 1995.; Toland, John. The Rising Sun: The Decline and Fall of the Japanese Empire, 1936–1945. New York: Random House, 1970.
Mark Van Rhyn