the 3,7 was a good gun
the flak 88 was one of the best pieces of artillery in the world
Both the US and Great Britain both had AAA gun systems not dissimilar to the much vaunted German 88mm Flak gun. But as has been pointed out, it seems that only the Germans bothered to train their crews and develop ammunition so that the 88mm could be used as a superb anti-tank gun as well as a direct fire artillery piece so infamous to the Allies.
So, why did the Western Allies not do the same. Why was the US M3 90mm AAA gun not really feared by the Germans on the ground unless it was mounted in an M10 GMC or M26 Pershing? In addition, the Brits had a 3.7 inch gun that looks even more formidable…
I’m not sure the statement about Allies not training AA crews for AT fire is accurate. At least, the US seems to have made frequent enough use of the AA 90mm M1s and M2s that crews used to nickname themselves/boast of being a “triple threat” - referring to their use as AA, AT, and a plain old field artillery (IIRC, the Germans also used their Flak 88’s in the last capacity). And I certainly have seen several different photos of US 90mm AA guns in AT positions. Maybe the same level of attention/credit to US crews isn’t as widely promoted because they weren’t as “novel” as the German use of the Flak 88 was? Or, perhaps the 88’s reputation as a tank killer was made against comparatively thin-armored vehicles, and in the late war (post-6/6/44) ETO, when US guns became available in significant numbers, they were simply not “as” effective because tanks were better protected by then?
Regarding British use – and I may be thinking of a discussion about a different gun, so I could easily be wrong – I do seem to remember that the British 3.7 gun was both heavy/difficult to move, and that almost all such guns were retained for the defense of the British Isles.
For what it is worth, the Soviets (85mm M1939) and the Italians (M 90/53; Axis, I know this was about Allies, but thought I’d toss it in because I’ve seen posters elsewhere that seem to think only Germans used AA guns in a AT role.) also used their medium AA guns in an AT role on occasion, though I don’t know how much training they may have received for this role. In the case of the Italians, their shortages meant the AA guns were pretty much used only in locations where AA defense was needed, so they were used AT only in the comparatively rare circumstance that armor fighting was occurring near their station (though a few where mounted on trucks to become an SP, and there was also the Semovente 90/53); I understand the gun was very comparable to the Flak 88 models in terms of AA effectiveness. About Soviet usage of the M39 I know much less, and have seen just a few scattered pictures of the gun in AT mode. I have gotten the impression that AT use of the weapon was infrequent, but don’t know the reason. I don’t know if the exact gun was used for an AFV’s main weaponry or not, either… The Japanese also used their 75mm AA gun in AT role, and it is described by some as the best AT weapon they had – though again, I don’t know how much specific training they had for the role.