Shortround6
Major General
So where were the fighter bombers when in 1940/41 the European combatants suddenly discovered that they needed them?
hiding in disguise
Why did they have to press their established fighter aircraft and in the German case Zerstorer, into service to fulfil that role?
Because that is what a fighter-bomber is, it is a fighter with bomb racks/mounts underneath, it is NOT a special type of aircraft. The bomb racks cause drag and a loss of performance if fitted at all times. Germans were able to fit bomb racks to 109Es and make a creditable fighter bomber for 1940 even if not ideal.
British, if they hadn't had their thumbs stuck up their bums about constant speed props for so long might have been able to experiment with the fighter bomber concept a bit sooner. Fixed pitch props and throttled back engines for take-off aren't the best recipe for taking off with heavy loads. It is a fair bet that even those 1934 biplane Hawks had at least a variable pitch prop.
A little later the Americans also discovered that they needed such aircraft themselves. If the need had been foreseen I would suggest that suitable aircraft would have been available. Instead, once again, fighters were adapted to the role. Both the P-47 and P-51 had been designed for a very different role at a very different altitude.
Americans had had such planes right up until 1939/40. The P-26 Peashooter could carry 200lbs and the P-35 could carry 350lbs. The question is why this capability went away with the P-39 and P-40, especially since we KNOW that in the P-40s case the drawing and tooling existed for the racks/bomb mounts, the control runs and the panels/boxes for the cockpit.
The Army had, during the 1930s bought about 100 fixed landing gear Northrop A-17 attack aircraft and about 100 retractable landing gear A17As, By the start of WW II (1939) it was planed to replace the remnants of these aircraft with twin engine attack bombers (A-20s). The Army had also decided they wanted air cooled engines for ground attack planes. This may explain the deletion of bomb racks from the V-12 powered P-38-P-39-P-40. Once the shooting started the Army, like the British and many other countries, was forced to use what they could get (what was in production) rather than what was on their wish list.
.The Hawk, Lysander etc fall into a broad category, maybe not the literal British one, of Army Cooperation aircraft. They were not viable as fighters in 1939
I am not surprised that the Hawk III Biplane was not a viable fighter in 1939. The Hawk 75 certainly was as shown by it's performance in France in 1940 and by it's use in Finland. The fitting of the bomb racks/controls would have done little to change that.
I don't know enough about Japanese aircraft, doctrine or tactics to have an opinion about them
The light bomb loads may not have been very effective (but with 700hp engines heavy loads were out of the question) but the point is that fighters carrying bombs to drop on targets close to bases were certainly not a new or unusual concept in 1939-40-41. Various air forces might argue about doctrine or resource allocation but few professional air forces could claim ignorance of the practice and it it was over 20 years since it was throw a few bombs over the side of the cockpit. Germans had hundreds of Arado 68s and He 51s with their six 10kg bomb installations. in the mid 1930s. Why there was no rack on the 109 I don't know.