Something to start considering this issue
https://en.wikipedia.org/wiki/Bomber_Mafiarockets DID take down light bridges and "light" doesn't necessarily mean "wood"
folk forget exactly how fast those RP-3 rockets were going when they hit, their mass/design
as was often pointed out it's the equivalent of a broadside from a destroyer. Anyone think a destoryer salvo wouldn't cause serious harm to a light bridge, hm?
American "Tiny Tim" rockets were more powerful and so much more likely to wreck such a structure but alas weren't very accurate
still, rockets were MUCH more accurate than bombs
exceptional pilots could use skip bombing though to very great effect and accuracy it should be said but those DO require suitable aircraft, NOT heavy bombers
remember, if you have numerous aircraft firing those rockets at shallow angle, the odds are much higher you will hit and do damage, enough damage the structural integrity gets compromised
whether the bridge drops, or, the weight of the next train going over collapses it, or it's left "unsound" and thus taken out of service until repaired, it's much better than mass bombing that get sno result
bombs were mostly useless, because they almost never hit, except when dropped by a dive bomber or very skilled fighter bomber pilot
the colossal loss in pilots, expensive aircraft etc in the "bomber mentality" was absolutely INSANE in WW2, exactly the same with the stupidity of tossing men against trenches in WW1
as I've noted, what is grossly, criminally overlooked, is the expense of those men (each man's training was worth FAR more than a typical bomber) and as people, these were often the brightest and best and losing them was terrible damage to the nation in the long term.
NOTE: British bomber crews had worse death rates than infantry in WW1
The definition of insanity is doing the same thing over and over again, but expecting different results
so, until you have a reliable accurate guided weapon, what would you do? wait years while doing nothing to the enemy?!
0.5 cals were too light really especially when they started armouring trains purely to protect them (not "armoured military trains", merely adding sheet steel, angle iron etc around the boilers)
America had a serious screw up in production of the 20mm cannon and then blockheads refused to fix this, so US forces had ot use inferior .50 cals which were good for somethings, but didn't have the power vs light armoured vehicles etc.
Though, Japanese aircraft were extremely lightly constructed with almost no defensive protections what so ever and thus .50 cal was perfectly good vs them
https://en.wikipedia.org/wiki/Hispano-S ... production