The recent 7:10 to Tokyo article, Unexploded WWII Bombs In Japan- How Many Are Out There?, provoked some interesting responses but it came as a bit of a surprise to hear from someone who was actually on the ground in Japan disposing of these remnants from WWII.  Roy Kasier took an interest this article and provided a lot of food for thought in his well-researched comments. Roy had a fifteen year career in Explosive Ordnance Disposal (EOD) for the US Army and spent three of those years (1967-1970) at Ikego Army Ammunition Depot in Kanagawa Prefecture.  He has generously agreed to share some insights on how bombs work, how they are disposed of and has provided some interesting newspaper clippings from the time. Roy retired in 1976, after 24 years of service. He often recalls the time he served with the 97^th and fondly remembers the great guys he served with.

The 97^th Explosive Ordnance Disposal (EOD) was the last US Army Explosive Ordnance unit stationed in Japan (deactivated in 1970) and was based in Zushi City, about 40 kilometers (25 miles) outside of Tokyo.   Roy was assigned to this unit from 1967 - 1970 and recalls participating in the disposal of three unexploded bombs (UXB) during that period.   In his comments on Unexploded WWII Bombs In Japan- How Many Are Out There?, he states that between November 1, 1944 and August 15, 1945 American B29 Superfortresses dropped more than 11,000 bombs, weighing 500 pounds or more, on Tokyo alone, destroying 51% of what is now the worlds largest city.  Historically 5-20% of military high explosive munitions fail to function as intended (duds). Given those failure rates somewhere between 500 and 2,200 unexploded bombs would have been left behind after WWII.

So why didn’t theses bombs detonate?  Roy explains that the general purpose, high explosive, bombs that were dropped on Japan had three main types of fuses resulting in detonation on impact (nose and tail impact inertia fuse), detonation after surface penetration (tail impact inertia fuse), or delayed action detonation up to 144 hours after impact (tail fuse).

When a bomb is dropped an arming wire is normally withdrawn from the arming vane, which looks like a little windmill, and the vane then rotates a rod that arms the fuse which causes the bomb to detonate. If the bomb came out of the plane without the arming wires being extracted the bomb would impact the ground without detonating and would leave a penetration hole rather than an explosion crater.  Another possibility is that the bomb’s firing pin could fail to strike the detonator or get hung up by some type of obstruction, in which case the bomb could detonate with the least disturbance.  To further complicate matters, most bombs had an anti-withdrawal feature that prevents the adapter booster and fuse from being unscrewed from the bomb by a locking pin.  If an attempt was made remove this portion of the bomb, the licking pin would activate the fuse and the bomb would detonate.

After a bombing raid, Japanese civil defense officials would scour the area bombed to look for impact craters.  US UXB reconnaissance procedures would include probing the penetration hole with a long non-magnetic rod to determine the trajectory of the bomb and its final resting place. The location of the bombs would then be recorded on a map similar to the one that you see below.

Once an unexploded ordinance is located, a variety of different disposal methods are available to the EOD teams.  The decision is often a difficult one as there is a need to balance risk to the EOD team with magnitude of the damage that would result if the unexploded bomb were to detonate.  The options include remote on-site detonation, removal and transport to a remote destination for disarming and/or detonation, or a hands on disarming of the ordnance on-site.  The latter method carries the most risk for the EOD team and is only utilized to protect lives, very important property, materials, or facilities. The safest way to dispose of UXB is to evacuate the area, take measures to protect against blast damage, and then detonate the bomb in place. This option is usually not available in densely populated areas like Tokyo.

Tanashi, Tokyo, January 1969

A 500lb HE bomb was found with a M123 chemical long delay anti-withdrawal fuse.  The Japanese Ground Self Defense Force (JGSDF) asked the asked the Explosive Ordnance Disposal (EOD) unit from Ikego Army Ammunition Depot to take on the job of rendering the bomb safe.  It was determined that blowing up the bomb in place with a full scale detonation was not the best way to go because the bomb was located next to houses, a railway station and a hospital.

The commanding officer, Lt Lanier, recommended that a sand bag barricade be built around the bomb to reduce damage to the area in the event of a full-scale detonation or contain the damage that would result from a partial detonation. It took 60 men from JGSDF, 10 hours to fill 8,000 sand bags and erect the barricade based on the specifications of the American EOD team. Roy said “I was amazed when I saw the sand bag barricade. It was big!”

The Assistant EOD Supervisor of the 97^th SFC Albertson, a WWII EOD veteran who had retired and returned to active service, mentioned that sometimes the personnel fusing these bombs were in a hurry and failed to insert the locking pin in the adapter booster. This was a long shot but the team though it was worth investigating. Lt, Lanier and Roy climbed over the sand bag barricade and studied the bomb for a few moments. It was apparent that the bomb had been moved at some point and had not detonated so they decided to see if there was a locking pin. They applied gentle pressure to adapter booster in a counter clockwise direction, expecting to meet the resistance of the locking pin, but there was no resistance. It turned out that SFC Albertson’s long shot was right, there was no locking pin, and the adapter booster with fuse came right out of the bomb. It took just a few minutes render this 500 lb bomb safe!

Inokashira Park, Tokyo, 1969

Shortly after disposing of the Tanashi bomb the EOD team was told of another UXB that was in the process of being excavated in Inokashira Park about 20 minutes by train from Tokyo’s Shinjuku Station. It became a concern after another bomb in the park had detonated for no apparent reason. Excavation of the bomb was complicated by the fact that the site kept flooding with water. The JGSDF engineers excvated and 15 foot hole, reinforced it with metal pipes and set up a system to pump water from the excavation site.

A few days later the area was evacuated and the EOD team went to work.  First the discovered that someone had sawed off the arming stem adapter plug, which is one of the ways the EOD team identifies the type of bomb they are dealing with. Roy tells us that this and the jackhammers that were used around the bomb were “bad things to do” and says that it was fortunate that these efforts did not cause the bomb to detonate. He went on to say that “Since the bomb had been subject to so much rough treatment during the excavation without detonating, and the successful experience with the Tanashi bomb we thought a procedure from a WWII disposal manual was worth a try.”

Roy was at the control point that had been set up some distance from the bomb and was in constant contact with the technicians at the bombsite via wired communications.  This time the adapter booster was locked in and it took about 2 hours, several modifications of tools and several trips back and forth between the control point and the bomb site before the adapter booster and fuse were successfully removed and separated from the bomb.  The adapter booster, still containing the fuse was well sand-bagged and transported to Ikego Army Ammunition Depot where the fuse was remotely removed from the adapter booster and the adapter booster was destroyed.   A few days later, while stored under a sand bag, the fuse functioned, setting off the detonator.

The Bomb that Did a U-turn

The third UXB disposal that Roy participated in was pretty much routine and occurred some time prior to the incidents above. The only notable thing about this disposal for Roy was that the shaft dug to access the bomb went down and then off to one side in order to expose the tail of the bomb for disposal. The bomb had penetrated the ground, somehow made a U turn, and was pointed toward the surface!

The cost to dispose of the Inokashira Park bomb was $38,892 in 1969 which is over $220 thousand US dollars today and Roy explains how the decision to dispose of a bomb that has survived more than 50 years of earthquake activity, surrounding construction and the daily rumblings of train and automobile traffic boils down to economic practicality and requires the careful consideration of the cost involved in the excavation and disposal versus the risk that the bomb will detonate.  Roy says that “Let sleeping dogs lie” is often the chosen approach until, for one reason or another, the unexploded ordinance becomes a present day problem as it did with the Chofu bomb that was the inspiration for the Unexploded WWII Bombs In Japan- How Many Are Out There? article.

Roy doesn’t believe that there should be a excessive concern surrounding unexploded bombs that still remain in Japan and says that the JGSDF EOD teams have proven their skill and professionalism in rendering safe and and disposing of unexploded ordinance time and time again.  He goes on to remind us that the Japanese are not alone, Britain and Germany also have the same problem resulting from the bombings that they were subject to during WWII.  Recent conflicts have brought a modern era UXO problem of cluster bombs and land mines to several other countries. Roy considers his 15 year career in EOD a “walk in the park” when compared to exceedingly more dangerous environment faced today by EOD personnel in Vietnam, Afghanistan an Iraq where they are often shot at, targeted by a roadside bombs, and have secondary bombs set up to detonate in the vicinity while the EOD team is responding to an incident.  He says that EOD personnel have become prime targets and their job is much more difficult and stressful that when he did it back in 1969.

I would personally like to thank Roy for sharing his insights into the fascinating subject and tip my hat to all of the current and retired EOD technicians out there, in Japan and elsewhere, whose dangerous work allows all of us to go on with our daily lives safely.

Lastly, Roy reminds us all that if we ever come across an UXB, we should consider it armed and very dangerous. Do not disturb it and call local authorities immediately.

closeAuthor: Shane Sakata Name: Shane Sakata
Email: shanesakata@gmail.com
Site: http://www.nihonsun.com
About: a resident of Mihama in Chiba, about thirty minutes outside of Tokyo on the JR Keiyo Line. Shane grew up in Burnaby, British Columbia, Canada and then moved with her husband to his home state of Hawaii in 1994, which is where she calls home when she’s not in Japan. From Hawaii it was on to Japan where she spent the better part of four years from 1994-1998. She is now back in Japan and writes about Japan travel & culture at The Nihon SunSee Authors Posts (2)