John K. Gailbraith lead a team of economists who performed a post war assessment of the effects of Allied bombing on the German economy. They minimized its effectiveness, an opinion that became fashionable in academic circles. This conclusion was in line with Soviet propaganda which was dismissive of the Western Allies in general, and the air campaign in particular.
In point of fact, German air defenses tied up 2,000,000 well armed and well equipped men, roughly the equivelant of 150 divisions. If the men and equipment used to fight off the Allied Air Forces had been available on the Eastern Front, the battles of Stalingrad and Leningrad might have been much different. Without air supremacy, D-Day would not have been possible and hundreds of Wehrmacht divisions tied down in the defense of the western coasts of Europe would have descended instead on Moscow.
Air defenses aside, the effects of the air campaign, especially against synthetic fuels and petroleum facilities was actually very effective. According to a Rand study report, by the end of the war German artillery shells were loaded with half salt and half high explosive, for instance. Many American, British, Canadian and Soviet infantry survived the war because of the ineffectiveness of German artillery at the end of the war.
During the Battle of the Bulge, the German plan explicitly depended on refueling tanks with captured petroleum. (Hell of a logistics system you got there, Adolf.)
Soviet behavior belied their propaganda. They made an exact bolt for bolt, nut for nut copy of the B-29, based on models which had been interned in the Soviet Union after making emergency landings after raids on Japan. (The Russians didn’t enter the war against Japan until after Hiroshima. Thanks for the help, fellas.) Stalin was all too aware of the decisive role of air power (even without atomic bombs) and wanted to discourage the U.S. from widening its lead and advantage over the Soviets.
Thanks LiM!