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With WWII era bomb sights only area targets can be hit from 20,000+ feet using iron bombs.
Very little prior to spring of 1944. There were a few notable exceptions such as bombing of Hamburg during July 1943 and Alkett during November 1943 but most pre-1944 Allied bombing raids were failures.
Fair summary.
One may add that the prospect of high altitude bombing triggered Germany to invest a HUGE amount of ressources into engeneering efforts trying to develop high altitude engagement solutions. These included Jet and rocket propelled A/C, several big gun AAA (15cm) projects, SAM and conventional but highly specialised high altitude interceptors like Ta-152H. Usually, these investments in R&D returned low or no benefit when the B29 just didn´t made advent.
It was worse than of the scatter of bombs within the bomb pattern) was 620 yards.
The RAF achieved a density of 10 bombs per acre at the centre of the bomb pattern. Only 30% of the ground at the centre of the pattern was cratered. In the opinion of the ORS the destructive effect of a high explosive bomb extended little beyond the crater, and this density was 'unimpressive'.
This is bombing from a relatively low altitude in day light. It is also a report on the ability of heavy bombers to operate in a ground support role where they were hoping that that.
An analysis of the bombing in support of the allied landings post D-Day by the RAF heavies, mostly carried out from 12,000 and 13,000 feet, showed an average displacement of the mean point of impact of 420 yards. The average radial standard deviation of the bomb pattern (a measurement they would destroy very small targets like individual guns and their emplacements.
Results for the USAAF were similar but slightly worse.
From higher altitudes both these figures would be larger but still in the hundreds of yards. Area bombing could most definitely hit an area the size of a small city or town and with the advent of master bombers and other marking techniques to adjust the aiming point (unlike USAAF bombers every RAF main force bomber had a bomb sight and was expected to use it, you can't bomb on someone else's say so at night) and with several hundred bombers attacking, large areas could be, and were, devastated.
Cheers
Steve
My question wasn't about the response cost, but what actually it could achieve in terms of physical damage. It seems to me that bombing from that altitude is going to be lucky to even strike a city that isn't as large as Berlin or London. I'm aware that the Germans historically were worried about it, but in terms of actually accuracy did they really have anything to be worried about (short of an Atom bomb which was dropped from 30,000 feet).
Steve - there were good technical reasons for 8th AF Lead Crew methods. Simply put the burden of bombing accuracy on the shoulders of the proven best bombardier's shoulders. The RAF methodology was what 8th practiced in 1942 and Lemay's lead crew concept immediately improved overall accuracy, but more importantly it improved specific target (i.e. the Cat cracker analogy I used earlier) destruction probability.
When every squadron focused on a high value target within a complex, the probability of critical hits were improved.
The RAF had very good bombsights but I question the 'every man do his thing' concept that 8th AF discarded two years before.
Alkett was seriously damaged during the "Battle of Berlin", one of the most effective bombing raids of the war. Was that intentional or did the RAF just get lucky that night?
Every man had to do his own thing because the majority of raids were at night when it is obviously impossible to fly formation and bomb on the say so of a lead bombardier. Bennett once claimed that less than half main force crews were bothering to do so!
The ORS looking at the support missions post D-Day thought that the US system was one of the principal reasons that the USAAF bomb patterns were less concentrated, if only by a small margin.
Again I must emphasise that these ORS were looking at the ability to destroy individual small targets with the heavy bombers, things that required a more or less direct hit, hence the importance of bomb density. This would not apply to a target like a refinery or factory complex, though it would apply to something like a machine tool.
Cheers
Steve
Steve - my comments were directed toward daylight raids conducted by RAF in 1944/1945.
IIRC the ORS looked at all 8th AF raids including H2X (blind bombing as far as 8th concerned) directed bombing through 10/10. The 8th never attained the same proficiency as the RAF for such attacks.
In almost every case the 8th went back to those targets in better visibility.