09. 8月 2045 - 3:50

Nakasaki Carbeque! | 水曜日, 09. 8月 2045

Responsibility for the timing of the second bombing was delegated to Tibbets. Scheduled for 11 August against Kokura, the raid was moved earlier by two days to avoid a five-day period of bad weather forecast to begin on 10 August.[139] Three bomb pre-assemblies had been transported to Tinian, labeled F-31, F-32, and F-33 on their exteriors. On 8 August, a dress rehearsal was conducted off Tinian by Sweeney using Bockscar as the drop airplane. Assembly F-33 was expended testing the components and F-31 was designated for the August 9 mission.[140]

At 03:49 on the morning of August 9, 1945, Bockscar, flown by Sweeney's crew, carried Fat Man, with Kokura as the primary target and Nagasaki the secondary target. The mission plan for the second attack was nearly identical to that of the Hiroshima mission, with two B-29s flying an hour ahead as weather scouts and two additional B-29s in Sweeney's flight for instrumentation and photographic support of the mission. Sweeney took off with his weapon already armed but with the electrical safety plugs still engaged.[142]

During pre-flight inspection of Bockscar, the flight engineer notified Sweeney that an inoperative fuel transfer pump made it impossible to use 640 US gallons (2,400 l; 530 imp gal) of fuel carried in a reserve tank. This fuel would still have to be carried all the way to Japan and back, consuming still more fuel. Replacing the pump would take hours; moving the Fat Man to another aircraft might take just as long and was dangerous as well, as the bomb was live. Tibbets and Sweeney therefore elected to have Bockscar continue the mission.[143][144]
This time Penney and Cheshire were allowed to accompany the mission, flying as observers on the third plane, Big Stink, which was flown by the group's operations officer, Major James I. Hopkins, Jr. Observers aboard the weather planes reported both targets clear. When Sweeney's aircraft arrived at the assembly point for his flight off the coast of Japan, Big Stink failed to make the rendezvous.[142] Though ordered not to circle longer than fifteen minutes, Sweeney continued to wait for The Big Stink, at the urging of Ashworth, the plane's weaponeer, who was in command of the mission.[145]

After exceeding the original departure time limit by a half hour, Bockscar, accompanied by The Great Artiste, the support B-29 flown by Captain Frederick C. Bock, proceeded to Kokura, thirty minutes away. The delay at the rendezvous had resulted in clouds and drifting smoke from fires started by a major firebombing raid by 224 B-29s on nearby Yawata the previous day covering 70% of the area over Kokura, obscuring the aiming point. Three bomb runs were made over the next 50 minutes, burning fuel and exposing the aircraft repeatedly to the heavy defenses of Yawata, but the bombardier was unable to drop visually. By the time of the third bomb run, Japanese antiaircraft fire was getting close, and Second Lieutenant Jacob Beser, who was monitoring Japanese communications, reported activity on the Japanese fighter direction radio bands.[146]

By the time they reached Kokura a half hour later, a 70% cloud cover had obscured the city, inhibiting the visual attack required by orders. After three runs over the city, and with fuel running low because a transfer pump on a reserve tank had failed before take-off, they headed for their secondary target, Nagasaki.[142] Fuel consumption calculations made en route indicated that Bockscar had insufficient fuel to reach Iwo Jima and would be forced to divert to Okinawa. After initially deciding that if Nagasaki were obscured on their arrival the crew would carry the bomb to Okinawa and dispose of it in the ocean if necessary, Ashworth ruled that a radar approach would be used if the target was obscured.[147]

At about 07:50 Japanese time, an air raid alert was sounded in Nagasaki, but the "all clear" signal was given at 08:30. When only two B-29 Superfortresses were sighted at 10:53, the Japanese apparently assumed that the planes were only on reconnaissance and no further alarm was given.[148]

A few minutes later at 11:00, The Great Artiste dropped instruments attached to three parachutes. These instruments also contained an unsigned letter to Professor Ryokichi Sagane, a nuclear physicist at the University of Tokyo who studied with three of the scientists responsible for the atomic bomb at the University of California, Berkeley, urging him to tell the public about the danger involved with these weapons of mass destruction. The messages were found by military authorities but not turned over to Sagane until a month later.[149] In 1949, one of the authors of the letter, Luis Alvarez, met with Sagane and signed the document.[150]
At 11:01, a last minute break in the clouds over Nagasaki allowed Bockscar's bombardier, Captain Kermit Beahan, to visually sight the target as ordered. The Fat Man weapon, containing a core of about 6.4 kg (14 lb) of plutonium, was dropped over the city's industrial valley at 32.77372°N 129.86325°E. It exploded 43 seconds later at 469 m (1,539 ft) above the ground halfway between the Mitsubishi Steel and Arms Works in the south and the Mitsubishi-Urakami Ordnance Works (Torpedo Works) in the north. This was nearly 3 km (1.9 mi) northwest of the planned hypocenter; the blast was confined to the Urakami Valley and a major portion of the city was protected by the intervening hills.[151] The resulting explosion had a blast yield equivalent to 21 kt (88 TJ). The explosion generated heat estimated at 3,900 °C (7,050 °F) and winds that were estimated at 1,005 km/h (624 mph).[152] Casualty estimates for immediate deaths range from 40,000 to 75,000.[153][154][155] Total deaths by the end of 1945 may have reached 80,000.[92]

Of 7,500 Japanese employees who worked inside the Mitsubishi Munitions plant, including mobilized students and regular workers, 6,200 were killed. Some 17,000 others who worked in other war plants and factories in the city died as well.[156]

Unlike Hiroshima's military death toll, only 150 soldiers were killed instantly, including thirty-six from the IJA 134th AAA Regiment of the 4th AAA Division.[88][157] At least eight known POWs died from the bombing and as many as 13 POWs may have died, including a British citizen, Royal Air Force Corporal Ronald Shaw,[158] and seven Dutch POWs.[159] One American POW, Joe Kieyoomia, was in Nagasaki at the time of the bombing but survived, reportedly having been shielded from the effects of the bomb by the concrete walls of his cell.[160] The radius of total destruction was about 1 mi (1.6 km), followed by fires across the northern portion of the city to 2 mi (3.2 km) south of the bomb.[161][162]

About 58% of the Mitsubishi Arms Plant was damaged, and about 78% of the Mitsubishi Steel Works. The Mitsubishi Electric Works only suffered 10% structural damage as it was on the border of the main destruction zone. The Mitsubishi-Urakami Ordnance Works, the factory that manufactured the type 91 torpedoes released in the attack on Pearl Harbor, was destroyed in the blast.[163]

Because of the delays in the mission and the inoperative fuel transfer pump, the B-29 did not have sufficient fuel to reach the emergency landing field at Iwo Jima, so Sweeney flew the aircraft to Okinawa. Arriving there, he circled for 20 minutes trying to contact the control tower for landing clearance, finally concluding that his radio was faulty. Critically low on fuel, Bockscar barely made it to the runway on Okinawa's Yontan Airfield. With only enough fuel for one landing attempt, Sweeney and Albury brought Bockscar in at 150 miles per hour (240 km/h) instead of the normal 120 miles per hour (190 km/h), firing distress flares to alert the field of the uncleared landing. The number two engine died from fuel starvation as Bockscar began its final approach. Touching the runway hard, the heavy B-29 slewed left and towards a row of parked B-24 bombers before the pilots managed to regain control. The B-29's reversible propellers were insufficient to slow the aircraft adequately, and with both pilots standing on the brakes, Bockscar made a swerving 90-degree turn at the end of the runway to avoid running off the runway. A second engine died from fuel exhaustion by the time the plane came to a stop. The flight engineer later measured fuel in the tanks and concluded that less than five minutes total remained.[164]

Following the mission, there was confusion over the identification of the plane. The first eyewitness account by war correspondent William L. Laurence of the New York Times, who accompanied the mission aboard the aircraft piloted by Bock, reported that Sweeney was leading the mission in The Great Artiste. However, he also noted its "Victor" number as 77, which was that of Bockscar, writing that several personnel commented that 77 was also the jersey number of the football player Red Grange.[165] Laurence had interviewed Sweeney and his crew in depth and was aware that they referred to their airplane as The Great Artiste. Except for Enola Gay, none of the 393d's B-29s had yet had names painted on the noses, a fact which Laurence himself noted in his account, and unaware of the switch in aircraft, Laurence assumed Victor 77 was The Great Artiste,[166] which was in fact, Victor 89.[167]

03:49am Nagasaki Time