Answer:
The German Assault of Stalingrad was a crushing defeat for the Germans because the Germans had to surrender and their entire Sixth Army. These troops, considered their best, were all lost. This battle was a turning point because there was a tremendous amount of deaths in this battle alone, this battle completely changed Germany's morale about the war, and the Germans had finally lost a big battle which turned the war into the favor of the Allies. The last German troops in the Soviet city of Stalingrad surrender to the Red Army, ending one of the pivotal battles of World War II. This began one of the most horrific battles of World War II and arguably the most important because it was the turning point in the war between Germany and the USSR.
I hope this helps you!!! I love German history (probably because I am currently taking a German class : }