Blowing up bridges

In many WW2 theatres the use of railways was critical to the maintenance of logistics, and thus became a target for the opposing side. A key weakness of the rail network was the rail bridge, if destroyed, it was both time and material costly to repair, and effectively closed a logistical line down.

How to destroy the enemy’s bridges was always the question, and airpower played its part, however bombing wasn’t very accurate, at high altitude it was pure luck than anything else that a bridge was hit, even if carpet bombed, while low level, although it could be more effective, was also much more costly for the air force attacking. The length of bridge also played a part, the bigger the better. So, if you were going to attack a line of communications, ideally you picked the biggest rail bridge, because it would be the most difficult to repair. Knowing this the defending side would ensure it was well defended with AA guns.

However, an alternative way of attacking these lines of communications was by way of the saboteur, who could be a resistance fighter, or a soldier smuggled in by air, sea or torturous land route. However, these forces were constrained by a lack of ability to overcome the forces defending a bridge and their restrictions on the amount of explosive they could carry.

So, their main target was the smaller bridge, a single span, either not defended or just by a watchman, maybe a routine patrol, which would still close down a line of communications, but could be restored quicker. And lastly, their extraction after blowing a bridge up was also problematic. Looking more closely at this option, and expecting most single span bridges of this period to be a truss bridge built of steel, what are the weak points of this bridge, how easy is it to destroy, and what size, weight of explosive might be required.

Regards
Fatboy Coxy

 

This was a lot harder than it looked. Important bridges were guarded. If it was an important railway, all bridges were important. OB West made a weekly report. In the week before D Day there were - reported In the week before D Day. Do you know what proportion of bridges were destroyed by sabotage as opposed to air attack?

I am not sure how much advice anyone should give online to someone making a casual inquiry about how to blow up a specific type of bridge.

Try searching for a military engineering manual online
FM 5-250 Explosives and Demolitions 1992 : Free Download, Borrow, and Streaming : Internet Archive

 

In the movies it always seemed like blowing up bridges were always successfully accomplished with the star walking off into the sunset...

 

Just expanding on the idea of a saboteur type attack, a night attack might be preferable as less chance of discovery, but this must be weighted up against working in darkness. Around the time of a full moon might be the best compromise. Secondly assuming you’re a small unit of 4-6 people, leaving 1-2 on lookout, 3-4 have to carry the explosives onto the bridge, place and wire them up, running the wires back to a detonator. This must be quite time consuming; I wonder how long it might take. And thirdly, the explosive must have been carried by a nondescript car/van, horse cart or pack mule, so weight of explosive will limit the amount available.

Thanks, manual very informative.

Working on the idea that the British operation Matador, December 1941, did take place, what possibilities were there for them to destroy railway bridges in the Kra Isthmus, on the Thai rail line Bangkok to Hat Yai. would have made a mess of Japanese logistics, especially if Matador had been successful, and the port of Singora captured.

Regards
Fatboy Coxy

 

Beau, actually!

 

Try Tallboy bomb. Just the earthshake it created is enough. Though it was not usable early in war.

 

..also-I would think the ''important'' bridges were bigger/longer/heavier/sturdier/solid/etc? = much harder to destroy.....they have to be damaged to the point where it's not easy to repair = that takes a lot of power and knowledge ...you can't have any partisan doing it

 

The Germans mined and wired most bridges that were within striking distance by the enemy. In the last third of the war, our main problem was to keep the bridge intact, not blow it. The 15th USAAF blew a lot of bridges in Italy but the Germans were still able to get supplies and reinforcements down south. For the problems of hitting a bridge by aircraft, one might look at the problems we had with the Ben Hoa bridge in N. Vietnam.

 

This has enormous merit, your spot on the extra weigh would help by providing more stress on the bridge at the time its blown, hopefully helping pull a span down. This would work better with a train, than a road convoy, in part weight, and in part, everybody's on the train, no small advance guard checking the bridge beforehand. Of course its a lot more stressful for the bridge blowers! and you wonder how often trains cross, cant be too often, as they need time to wire up the explosives, but you cant wait a day or so, South East Asia is a very humid, not good for the explosives the British used at the time, I believe.

Regards
Fatboy Coxy

 

If you have read the small high voltage booklets or you know my meaning, the train went into a tunnel which was blown.

 

I wouldn't think it to be very high, having enough explosive would be the first problem, let alone getting to the bridge and wiring it all up undiscovered.

 

.for a ''large''/solid/etc bridge, I don't think that amount of explosives would do it--per my post in this thread ...you have to know where to put the explosives

..I would think it to be very, very difficult to judge the correct explosive amount in just '''disrupting the structural integrity of the span''' ..too little and it's worthless..you have to put in more..either you have to put a lot in there, or you might not ''disrupt'' the integrity

...that must be a big pack pack if a '''solid''' bridge
..Hogan's Heroes took down some bridges, didn't they?

What finished the bridge at Remagen?

....maybe I'm wrong....there must be someone here that can give specifics ...they took out bridges in the Battle of the Bulge

..one of my favorites books The Damned Engineers book talks about the engineers and bridges ......they destroyed the Trois Ponts bridge, I think

Defense at Trois-Ponts, Company "C" 51st Engineer Combat Bn

definitely not solid


what about this one?

 

here they say they used 1000lbs

bold mine

a 1000lb bomb will do a lot of damage
...''excessive''' = per post # 17
..''''nothing like an Engineer School solution''' = per my first post = you need to know what you are doing...
...maybe 100 lbs would be an ''engineer school solution''..????..
...CRIBA Home

 

The bridges I was talking about were specifically railway bridges, of the metal truss construction type. I think OpanaPointer is with me on the idea that you don't necessarily have to destroy the bridge in its entirety, although that would be nice, but weaken it's ability to support itself, and so collapse a span. This would be done by 'cutting' metal trusses, which spread the weight, at a cost efficient use of the explosives. You are quite right that it would need someone who knows what they are doing.

If you failed in bringing down the span, you may still have disrupted the structural integrity,meaning the bridge cannot take a trains weight, and has to be fixed. How quickly this can be done is dependant on a number of things but the rail line would be effectively cut for several days, if not weeks.

 

...unless there is major damage, I would think repair would not take long...so as I said in a previous post--the damage has to be enough--not just a little....you say ''weaken''' = if you weaken it enough so it collapses, that's a lot of damage...what do you mean by ''weaken''?
..if I'm not mistaken, engineers make it [ made them ] so bridges/etc will not collapse from ''''minor'' damage/problems.....it won't for sure collapse with a break here or break there unless it's a very critical area