As to 'Flak Batteries' in the context of the East - they were deployed as anti-tank batteries but the deployment of critical additional AAA capability of 88 and 128mm were to the key cities and industrial areas to the detriment of deployment to the East where they were most needed to stop Soviet armor.
8,8cm Flak was integral to TOE of Panzer Division since war begun in 1939. They were never meant to be primarly ground weapons, but used on occasion with great success because of some properties that were advantagous (good ballistics). It was an anti aircraft gun, after all.
12,8cm Flak was never deployed on front, they were rare, their high altitude performance was complete unneccsary.
BTW, the 8,8cm Flak was quite cheap compared to building thousends of bombers. One FlaK 18 costed 33 000 RM, whereas a Bf 109 ca. 45 000, and a He 111 around 250 000. I suppose a viermot in German, like He 177, would cost at least 500-600 000 RM, now please compare that to cost of gun. For every heavy bomber price, you could build 20(!) heavy Flak...
Also there seem to be hardly increasing preference to Luftwaffe (mainly guns at home defence, but also some guns in frontline were directed under LW) to Heer. Receivence of Flak guns, by Heer and total production (% of total production Heer units received)
1941 : 126 / 1872 (6,7 %) - total production worth: 61 M RM,-
1942 : 176 / 2876 (6,1 %) - total production worth: 95 M RM,-
1943 : 296 / 4416 (6,7 %) - total production worth: 145 M RM,-
1944 : 549 / 5933 (9,2% ) - total production worth: 195 M RM,-
So, regardless of what Speer laments, truth is that Army received 50% greater share and almost twice the number of Flak guns in 1944, than in 1943... and as for costs, even at peak all 8,8 cm Flak gun production (to be fair, the cost is a bit higher because 10,5cm and 12,8cm guns were also produced) cost as much as a single of the Bismarck class ship (196 RM).
German Army bottleneck was never weapons, anyway. It was manpower, and fuel.. weapons they had more than enough.
I've seen the flak towers mentioned many times always was amused at the thought that peace-time apparantly saw the Hamburg tower converted into a nightclub.
Someone once said something similar to 'let our revenge be the laughter of the children' which sprang to mind.
Wien flaktower, on of them is converted to storage of modern art. I think its all well, because its safe, and modern art is so ugly anyway its better if locked away.
BTW it looks really weird in its surroundings. Huge (and I mean HUGE) concreate building in the midst of really nice park, with nice classical buildings around it.. then, this monstrosity. People who have house there must love that if they look out of window they just see an inductructable concrete wall.
