Day of “Wreckoning” for Osaka Arsenal

It came on Tuesday, 14 August 1945. Hitherto, the Osaka Army Arsenal had avoided catastrophic damage and was still in operation some 75 years after its establishment in 1870. As it provided some 20% of the Imperial Army’s ordnance, it was a lucrative target.

Images of the Osaka Army Arsenal, Osaka Hohei Kosho, circa 1914  (Courtesy National Diet Laboratory)
Images of the Osaka Army Arsenal, Osaka Hohei Kosho, circa 1914 (Courtesy National Diet Laboratory)

The Army Arsenal in Osaka had employed up to 60,000 workers across its vast complex near Osaka Castle. Tanks and artillery were among the many weapons of wear manufactured there. However, with the demands of war, e.g. military conscription, shortages of material, and relocation of production, by mid-1945 there was a great decrease in the workforce and productivity of the arsenal. Shortages were filled to some extent by forcibly-collecting workers and using student workers

Perhaps the exodus from Osaka following the death and destruction from air raids prior to 14 August also contributed to the lower number of workers. On the day of “wreckoning,” a false alarm earlier in the day delayed commuter trains, and reportedly only about 5,000 workers were present at around noontime on the day the end came. These workers were busy with assembling artillery and shell, anti-aircraft guns, shells, and even suicide submarines for the Navy.

The days leading up to the end of the war were stop and go for the American air forces, particularly the strategic bombardment forces with the B-29 Superfortress very heavy bombers. President Truman decided to suspend B-29 attacks on 11 August 1945, when Japan signaled an intent to end the war in the aftermath of the second nuclear attack and conventional B-29 raids on the night of 9/10 August and day on 10 August.

19th Bomb Group Superforts over Japan in 1945 - note Fujiyama in background.  Of note, the 19th Bomb Group was based at Clark Field in the Philippines when the war began in December of 1941.  (Twentieth Air Force Association,  Photo Courtesy of Ken Minsch (330th BG))
19th Bomb Group Superforts over Japan in 1945 – note Fujiyama in background. Of note, the 19th Bomb Group was based at Clark Field in the Philippines when the war began in December of 1941. (Twentieth Air Force Association,
Photo Courtesy of Ken Minsch (330th BG))

For Imperial Japan, 10 August was the “decisive day,” when Emperor Hirohito resolved the impasse between the civilian members of the “Big Six” of the Supreme Council for the Direction of the War. He decided that Japan must “bear the unbearable” and bring the war to a close by accepting the Allies Potsdam Declaration. Diplomatic cables were soon sent out to the Allies.

Imperial Conference of 9-10 August 1945 (US Army, MacArthur Reports, Plate No. 165)
Imperial Conference of 9-10 August 1945 (US Army, MacArthur Reports, Plate No. 165)

Weather conditions precluded bombing on 11 August, coincident with Truman’s directive to halt the B-29 raids. However, he allowed other conventional air operations to continue. This situation continued for a couple of days as the diplomatic back and forth played out. But with concern the militarists might seek to continue the war, Truman ordered USAAF and USN commanders to “…go ahead with everything we’ve got.” So on 14 August, the B-29’s flew to strike multiple targets in Japan. The 73rd Bomb Wing was tasked with Mission 326 to hit the Osaka Army Arsenal.

Capt. John R. Smolenski briefs members of the 500th Bomb Group on the mission to Osaka slated for 14 August 1945, their last combat mission of the war.  (US Army, via Fold3)
Capt. John R. Smolenski briefs members of the 500th Bomb Group on the mission to Osaka slated for 14 August 1945, their last combat mission of the war. (US Army, via Fold3)

The importance of Osaka’s Army Arsenal to Imperial Japan was stated in the target significance statement:

“The largest and most important single plant in the Empire engaged primarily in ground forces’ armament production. On the basis of its facilities, essentially a heavy arsenal, and, on the basis of its products, particularly important as a source of Army type heavy AA guns, including the 75 mm. and 88 mm. types believed manufactured exclusively here. It is also the principal producer of heavy field artillery and a major manufacturer of heavy shell cases. It is known to have produced, at various times, virtually every type of weapon used by the Japanese army, ranging from small arms and small mortars to the largest field pieces and railway guns.” (Target Significance statement for Osaka Army Arsenal, Target 90: 25-382 on Joint Target Group Target Information Sheet, 25 May 1945).

This aerial photograph was taken 27 February 1945.  It shows the vast Osaka Army Arsenal complex immediately to the East (right) and North (above) the Osaka Castle grounds and moats to the left in the picture.  It was the Imperial Japanese Army's largest arsenal.  (US Army, via Fold3)
This aerial photograph was taken 27 February 1945. It shows the vast Osaka Army Arsenal complex immediately to the East (right) and North (above) the Osaka Castle grounds and moats to the left in the picture. It was the Imperial Japanese Army’s largest arsenal. (US Army, via Fold3)

Situated in the northeast section of Osaka city. East and northeast of the adjacent Osaka Castle. The target area was irregular in shape, about 5,000 feet north to south and a maximum of 3,200 feet wide. It covered 13.1 million square feet in area, with the plant area (roofed buildings) about 40 percent of the site. The plant area was comprised of some 176 separate buildings with 5.3 million feet of floorspace. This followed a great expansion of the arsenal, much after 1941. The arsenal featured well-integrated metal processing plants with foundries and forges, machine shops and assembly facilities to make the weapons of war used by the Imperial Japanese Army.

Target Diagram for Osaka Army Arsenal created by the Joint Target Group identified the areas and individual buildings of the vast complex.  (US Army, via Fold3)
Target Diagram indicating fire susceptibility of the Osaka Army Arsenal created by the Joint Target Group identified the areas and individual buildings of the vast complex. (US Army, via Fold3)

Given the heavy industrial nature of the arsenal as a target, the big M66 2,000-pound general purpose (GP) bombs were used, as well as M65 1,000-lb GP bombs, with 1/40 second of a delay in fuzing on nose and tail fuzes. The average bomb load for B-29’s on this mission was 10.924 pounds.

One hundred and sixty one B-29’s were launched by the 73BW for the mission. The 21st and 506th Fighter Groups, based at Iwo Jima and both with P-51s, were designated as escort forces for the bombers on the daytime raid. Of the 161 Superforts, 145 bombed the arsenal and two aircraft hit targets of opportunity. Fourteen aircraft were non-effective.

The arsenal received 706.5 tons of bombs over a 45-minute period between 1416K and 1501K. The bombers attacked visually and released their ordnance from 22,100 and 25,100 feet.

Strike photos from 36 A/C carrying cameras showed excellent results, with 650 hits showing on the target. Of 843 bombs dropped, 216 hit within 1,000 feet of the aiming point.

About two-and-a-half minutes of a nearly four minute long home movie taken by Australian Army Brigadier (Brig) John O’Brien shows the extensive destruction of the arsenal wrought by the B-29’s (Brig O’Brien served as the Leader of the Australian Scientific Mission to Japan 1945-1946 and Chief of the Scientific and Technical Division Supreme Commander for the Allied Powers (SCAP) HQ Tokyo 1946-1951.) See the video on the Australian War Memorial website, at:
https://www.awm.gov.au/collection/F04956/

Flak was heavy, moderate generally accurate and continuously pointed, which damaged 26 B-29s. No enemy aircraft were sighted. Four B-29s landed at Iwo Jima. The average fuel reserve aboard returning Superforts was 954 gallons. The escort phase of the mission was flown without incident and all Mustangs of the escorting groups returned to base safely.

Picture taken from a B-29 Superfortress with P-51D Mustang fighter planes, perhaps the navigation ship for the  escort fighters enroute to Japan.  (Courtesy 506th Fighter Group.org)
Picture taken from a B-29 Superfortress with P-51D Mustang fighter planes, perhaps the navigation ship for the escort fighters enroute to Japan. (Courtesy 506th Fighter Group.org)

Bombing results indicated a highly effective mission in military terms. “Almost all the small machine shops and laboratories in central sections of arsenal were destroyed,” concluded the 73rd Bomb Wing’s Osaka mission report. “The large assembly type buildings and storage buildings in central and southern sections of plant were severely damaged or destroyed. Many direct hits visible on heavy machine shops at northern edge of arsenal.” Nearly 95 percent of the bombs burst within 3,000 feet of the aiming point.

First Lieutenant J. W. “Bill” Bradbury of the escorting 21st Fighter Group, 72nd Fighter Squadron recalled this last combat mission against Osaka: “We arrived off the coast of Honshu and joined the bomber stream to escort them over their target. They dropped their bombs, and we went back out over the ocean to join our three (navigator) B-29s. As we joined them and started flying back to Iwo Jima, one of the B-29s had picked up radio transmissions and came on the air saying, “Hey fellows, the war’s over.” I remember someone punching their mike button and replying, “Well the Japs sure as hell don’t know it.” He was referring to all the flak that was put up over the target against the bombers. We took about three¬-and-a-half hours to fly back to Iwo Jima and landed. Sure enough, the war was over.”

Back on the ground in Osaka, when the air raid siren sounded as the bombers approached workers evacuated the arsenal while air defense crewmember remained at their positions. The number of persons killed inside the arsenal was reportedly 382, much less than the 5,000 present. This does not include other casualties in the surrounding area or Osaka from the raid.

One particularly bad incident of collateral damage occurred at Kyobashi Station just north of the arsenal grounds around 1pm, which caused substantial loss of life and damage to the civilian-filled train station. Contributing to the loss was the fact that two trains had just arrived when the bombs were dropped. Why the trains were running during an air raid is unknown – perhaps railroad officials thought it was another false alarm. The error, in bombing accuracy and in failing to take shelter was costly – more than 210 dead civilians who could be identified and more than 500 unidentified people.

Kyobashi Station in Osaka, adjacent to the arsenal, seen in June, 1946, ten months after the 14 August 1945 raid.  (Courtesy Wikipedia)
Kyobashi Station in Osaka, adjacent to the arsenal, seen in June, 1946, ten months after the 14 August 1945 raid. (Courtesy Wikipedia)

So it was that one of the forges of Imperial Japan’s war machine came to an end. The arsenal’s grounds were later reborn as the Osaka Business Park and the Osaka Castle Park. Today the area has many high-rise buildings and is a center for business and entertainment.

And so ended the World War II air raids against Osaka. By one account, the human cost to Osaka from all the raids was about 15,000 people killed. Some 340,000 houses were destroyed, and an estimated 1.2 million people lost their homes and/or were driven from the city.

Namba area of Osaka City after the bombings of 1945. Nankai Namba Station is visible at left.  (Courtesy Wikipedia)
Namba area of Osaka City after the bombings of 1945. Nankai Namba Station is visible at left. (Courtesy Wikipedia)

That loss is significant, but against the scale of loss of life from 15 years of war in China and the Pacific, rather small: Imperial Japan suffered over 2 million military and 960,000 civilian deaths in the war, while her enemies lost over four million military and a staggering 25 million civilian lives lost (mostly Chinese) between 1937 and 1945.
Hopefully World War II was the last total war of humanity, though peace seems elusive in this chaotic world we live in. And those lives lost in Osaka, on the ground and in the air, should be remembered, not forgotten, to encourage all rational beings to find better ways to resolve conflict.

A few remnants of the Osaka Army Arsenal can be found today. One is just to the north side of the Osaka Castle grounds and moat.

Chemical Laboratory at the former Osaka Army Arsenal, circa 2007.  (Courtesy Wikipedia)
Chemical Laboratory at the former Osaka Army Arsenal, circa 2007. (Courtesy Wikipedia)

It is what was thought to be a “probable chemical laboratory” in Area “B” of the old arsenal, according to the Fire Susceptibility Plan for the arsenal drawn by the Joint Target Group in 1945.

Chart

Another remnant is what is described as a guard post

Guard post at the former Osaka Army Arsenal, circa 2007.  (Courtesy Wikipedia)
Guard post at the former Osaka Army Arsenal, circa 2007. (Courtesy Wikipedia)

There is also the remains of the Unloading Quay Gate.

Remains of the Osaka Army Arsenal Quay Gate, circa 2008.  (Courtesy Wikipedia)
Remains of the Osaka Army Arsenal Quay Gate, circa 2008. (Courtesy Wikipedia)

And a small but historically significant artifact is a monument to the Emperor Meji’s inspection of the Osaka Arsenal.

Photo of the monument to the Emperor Meiji's inspection of Osaka Imperial Arsenal, taken circa 2007.  (Courtesy Wikipedia)
Photo of the monument to the Emperor Meiji’s inspection of Osaka Imperial Arsenal, taken circa 2007. (Courtesy Wikipedia)

These remnants lie among the echoes of the war, reminders of the once mighty Osaka Army Arsenal, which ceased operations on the last day before the Second World War ended.
References

Osaka Army Arsenal (Osaka Hohei Kosho), at: http://www.ndl.go.jp/scenery/kansai/e/column/osaka_army_arsenal.html

Osaka Central Market, on the World War II Multimedia Database, at: http://worldwar2database.com/gallery/wwii1201

The Japanese armour and other vehicles thread, on the Tanks in World War 2 Forum, at: http://www.weaponsofwwii.com/forum/viewtopic.php?f=10&t=3130&start=20

Ruin of Imperial Army Osaka Arsenal (Osaka), at: http://wikimapia.org/14724482/ruin-of-Imperial-Army-Osaka-Arsenal

Mission 326 Summary, at: http://www.20thaf.org/missions/326.htm

Osaka Army Arsenal 20% source at: http://pwencycl.kgbudge.com/O/s/Osaka.htm

Total Osaka losses from air raids, at: http://japanfocus.org/-Yuki-TANAKA/2532/article.html

USAAF Chronology for August 1945, at: http://paul.rutgers.edu/~mcgrew/wwii/usaf/html/Aug.45.html

506th Fighter Group on Mission Number 51 (VII FC Mission #260) 14 August 45, at: http://506thfightergroup.org/iwotojapan.asp?ID=3#aug14

World War II casualties in the Pacific, at: https://en.wikipedia.org/wiki/Pacific_War
Images

Osaka Army Arsenal circa 1914, at:  http://www.ndl.go.jp/scenery/kansai/e/data/49/index.html

19th Bomb Group over Japan – Fuji in Background, at: http://www.20thaf.org/

Decision to Surrender at: http://www.history.army.mil/books/wwii/MacArthur%20Reports/macarthur%20v2%20p2/ch20.htm

P-51s with B-29, at: http://www.506thfightergroup.org/iwotojapan.asp

Kyobashi Station, June 1946, at: https://en.wikipedia.org/wiki/Bombing_of_Osaka#/media/File:Kyobashi_Station_Osaka_in_1946.jpg

Namba Station and area after the war, at: https://en.wikipedia.org/wiki/Bombing_of_Osaka#/media/File:Osaka_after_the_1945_air_raid.JPG

Osaka Arsenal chemical lab, at: https://commons.wikimedia.org/wiki/File:Osaka-Imperial-Arsenal-ChemiLabo01.jpg

Osaka Arsenal guard post, at: https://commons.wikimedia.org/wiki/File:Osaka-Imperial-Arsenal-Post.jpg

Osaka Arsenal Unloading Quay, at: https://commons.wikimedia.org/wiki/File:Osaka-Imperial-Arsenal-QuayGate.jpg

Emperor Meiji Monument at Osaka Arsenal, at: https://commons.wikimedia.org/wiki/File:Osaka-Imperial-Arsenal-GateMonument.jpg

2 thoughts on “Day of “Wreckoning” for Osaka Arsenal”

  1. Very thoughtful, diligent work. I’m not used to seeing quality accounts like this. This was my father’s last combat mission and one of his toughest of the war (497th BG/871st BS). The arsenal was protected by very concentrated flak and they nearly ‘bought it’. Flak bursts bracketed, then ‘walked’ into convergence on the plane. One of the 2000 lb. bombs did not release. They took it all the way back to Saipan, where it dropped through the doors and out of the plane the moment it touched down, at 130mph. All this knowing that the end of the war was a few hours away.

    Like

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