A matter of debate surely, but I think many point to the first or the second battle of El Alamein which was is June and late October of 1942
The first significant military setback for Hitler's forces was the Battle of Stalingrad, which occurred from August 1942 to February 1943. This battle involved the German Army's attempt to capture the city, ultimately leading to their encirclement and surrender against the Soviet forces. It marked a critical turning point in World War II on the Eastern Front.
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