Basically, the Russians refused to go up and fight. They concentrated on attacking the German ground troops. So, the Germans were forced to either come down and fight or stay high and watch their troops get attacked and killed.
They came down and fought, sometimes to their victory and sometimes to their defeat. In the end, the Russian learned from their mistakes and drove the Germans from Russian skies and lands. It's worth remembering that an enemy who doesn't care about the cost of victory is tough to defeat if his resources are deep enough.