On the day of the nuclear strike (August 9, 1945) the Boeing B-29 Superfortress Bockscar, commanded by Major Charles Sweeney, departed from Tinian's North Field just before dawn, carrying a plutonium bomb, code named "Fat Man".
The primary target for the bomb was Kokura, with the secondary target being Nagasaki, if the primary target was too cloudy to make a visual sighting. When the plane reached Kokura at 9:44 a.m. (10:44 a.m. Tinian Time), the city was obscured by clouds and smoke, as the nearby city of Yahata had been firebombed on the previous day - the steel plant in Yahata also had their workforce intentionally set fire to containers of coal tar, to produce target-obscuring black smoke. Unable to make a bombing attack on visual due to the clouds and smoke and with limited fuel, the plane left the city at 10:30 a.m. for the secondary target.
After 20 minutes, the plane arrived at 10:50 a.m. over Nagasaki, but the city was also concealed by clouds. Desperately short of fuel and after making a couple of bombing runs without obtaining any visual target, the crew was forced to use radar in order to drop the bomb. At the last minute, the opening of the clouds allowed them to make visual contact with a racetrack in Nagasaki, and they dropped the bomb on the city's Urakami Valley midway between the Mitsubishi Steel and Arms Works in the south, and the Mitsubishi-Urakami Ordnance Works in the north. 53 seconds after its release, the bomb exploded at 11:02 a.m. at an approximate altitude of 1,800 feet.
Less than a second after the detonation, the north of the city was destroyed and 35,000 people were killed. Among the deaths were 6,200 out of the 7,500 employees of the Mitsubishi Munitions plant, and 24,000 others (including 2,000 Koreans) who worked in other war plants and factories in the city, as well as 150 Japanese soldiers. The industrial damage in Nagasaki was high, leaving 68–80% of the non-dock industrial production destroyed. It was the second and, to date, the last use of a nuclear weapon in combat, and also the second detonation of a plutonium bomb.